Removes remaining snapshot backwards compatibility logic (#22512)

Previously, we removed all unneeded backward compatibility logic 
from the BlobStoreRepository because 6.0 does not need to support
2.x snapshot formats.  During the process of removing this backward
compatibility logic, some code was leftover that is no longer
necessary.  This commit removes all the remaining unnecessary
backwards compatibility code in BlobStoreRepository.

core/src/main/java/org/elasticsearch/repositories/blobstore/BlobStoreRepository.java

@@ -176,8 +176,6 @@ public abstract class BlobStoreRepository extends AbstractLifecycleComponent imp
 
     private static final String SNAPSHOT_CODEC = "snapshot";
 
-    static final String SNAPSHOTS_FILE = "index"; // package private for unit testing
-
     private static final String INDEX_FILE_PREFIX = "index-";
 
     private static final String INDEX_LATEST_BLOB = "index.latest";
@@ -373,7 +371,7 @@ public abstract class BlobStoreRepository extends AbstractLifecycleComponent imp
                 BlobPath indexPath = basePath().add("indices").add(indexId.getId());
                 BlobContainer indexMetaDataBlobContainer = blobStore().blobContainer(indexPath);
                 try {
-                    indexMetaDataFormat(snapshot.version()).delete(indexMetaDataBlobContainer, snapshotId.getUUID());
+                    indexMetaDataFormat.delete(indexMetaDataBlobContainer, snapshotId.getUUID());
                 } catch (IOException ex) {
                     logger.warn((Supplier<?>) () -> new ParameterizedMessage("[{}] failed to delete metadata for index [{}]", snapshotId, index), ex);
                 }
@@ -421,7 +419,7 @@ public abstract class BlobStoreRepository extends AbstractLifecycleComponent imp
         if (snapshotInfo != null) {
             // we know the version the snapshot was created with
             try {
-                snapshotFormat(snapshotInfo.version()).delete(snapshotsBlobContainer, blobId);
+                snapshotFormat.delete(snapshotsBlobContainer, blobId);
             } catch (IOException e) {
                 logger.warn((Supplier<?>) () -> new ParameterizedMessage("[{}] Unable to delete snapshot file [{}]", snapshotInfo.snapshotId(), blobId), e);
             }
@@ -439,7 +437,7 @@ public abstract class BlobStoreRepository extends AbstractLifecycleComponent imp
         if (snapshotInfo != null) {
             // we know the version the snapshot was created with
             try {
-                globalMetaDataFormat(snapshotInfo.version()).delete(snapshotsBlobContainer, blobId);
+                globalMetaDataFormat.delete(snapshotsBlobContainer, blobId);
             } catch (IOException e) {
                 logger.warn((Supplier<?>) () -> new ParameterizedMessage("[{}] Unable to delete global metadata file [{}]", snapshotInfo.snapshotId(), blobId), e);
             }
@@ -522,7 +520,7 @@ public abstract class BlobStoreRepository extends AbstractLifecycleComponent imp
             }
         }
         try {
-            metaData = globalMetaDataFormat(snapshotVersion).read(snapshotsBlobContainer, snapshotId.getUUID());
+            metaData = globalMetaDataFormat.read(snapshotsBlobContainer, snapshotId.getUUID());
         } catch (NoSuchFileException ex) {
             throw new SnapshotMissingException(metadata.name(), snapshotId, ex);
         } catch (IOException ex) {
@@ -533,7 +531,7 @@ public abstract class BlobStoreRepository extends AbstractLifecycleComponent imp
             BlobPath indexPath = basePath().add("indices").add(index.getId());
             BlobContainer indexMetaDataBlobContainer = blobStore().blobContainer(indexPath);
             try {
-                metaDataBuilder.put(indexMetaDataFormat(snapshotVersion).read(indexMetaDataBlobContainer, snapshotId.getUUID()), false);
+                metaDataBuilder.put(indexMetaDataFormat.read(indexMetaDataBlobContainer, snapshotId.getUUID()), false);
             } catch (ElasticsearchParseException | IOException ex) {
                 if (ignoreIndexErrors) {
                     logger.warn((Supplier<?>) () -> new ParameterizedMessage("[{}] [{}] failed to read metadata for index", snapshotId, index.getName()), ex);
@@ -563,27 +561,6 @@ public abstract class BlobStoreRepository extends AbstractLifecycleComponent imp
         }
     }
 
-    /**
-     * Returns appropriate global metadata format based on the provided version of the snapshot
-     */
-    private BlobStoreFormat<MetaData> globalMetaDataFormat(Version version) {
-        return globalMetaDataFormat;
-    }
-
-    /**
-     * Returns appropriate snapshot format based on the provided version of the snapshot
-     */
-    private BlobStoreFormat<SnapshotInfo> snapshotFormat(Version version) {
-        return snapshotFormat;
-    }
-
-    /**
-     * Returns appropriate index metadata format based on the provided version of the snapshot
-     */
-    private BlobStoreFormat<IndexMetaData> indexMetaDataFormat(Version version) {
-        return indexMetaDataFormat;
-    }
-
     @Override
     public long getSnapshotThrottleTimeInNanos() {
         return snapshotRateLimitingTimeInNanos.count();