Remove Outdated BwC Serialization in SnapshotInfo (#55451)

This is long outdated and can be removed in `8` now.

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/create/CreateSnapshotRequest.java

@@ -47,7 +47,6 @@ import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
 import static org.elasticsearch.common.xcontent.support.XContentMapValues.nodeBooleanValue;
-import static org.elasticsearch.snapshots.SnapshotInfo.METADATA_FIELD_INTRODUCED;
 
 /**
  * Create snapshot request
@@ -109,9 +108,7 @@ public class CreateSnapshotRequest extends MasterNodeRequest<CreateSnapshotReque
         includeGlobalState = in.readBoolean();
         waitForCompletion = in.readBoolean();
         partial = in.readBoolean();
-        if (in.getVersion().onOrAfter(METADATA_FIELD_INTRODUCED)) {
-            userMetadata = in.readMap();
-        }
+        userMetadata = in.readMap();
     }
 
     @Override
@@ -125,9 +122,7 @@ public class CreateSnapshotRequest extends MasterNodeRequest<CreateSnapshotReque
         out.writeBoolean(includeGlobalState);
         out.writeBoolean(waitForCompletion);
         out.writeBoolean(partial);
-        if (out.getVersion().onOrAfter(METADATA_FIELD_INTRODUCED)) {
-            out.writeMap(userMetadata);
-        }
+        out.writeMap(userMetadata);
     }
 
     @Override

server/src/main/java/org/elasticsearch/cluster/SnapshotsInProgress.java

@@ -50,8 +50,6 @@ import java.util.Objects;
 import java.util.Set;
 import java.util.stream.Collectors;
 
-import static org.elasticsearch.snapshots.SnapshotInfo.METADATA_FIELD_INTRODUCED;
-
 /**
  * Meta data about snapshots that are currently executing
  */
@@ -523,10 +521,7 @@ public class SnapshotsInProgress extends AbstractNamedDiffable<Custom> implement
             }
             long repositoryStateId = in.readLong();
             final String failure = in.readOptionalString();
-            Map<String, Object> userMetadata = null;
-            if (in.getVersion().onOrAfter(METADATA_FIELD_INTRODUCED)) {
-                userMetadata = in.readMap();
-            }
+            final Map<String, Object> userMetadata = in.readMap();
             final Version version;
             if (in.getVersion().onOrAfter(VERSION_IN_SNAPSHOT_VERSION)) {
                 version = Version.readVersion(in);
@@ -572,9 +567,7 @@ public class SnapshotsInProgress extends AbstractNamedDiffable<Custom> implement
             }
             out.writeLong(entry.repositoryStateId);
             out.writeOptionalString(entry.failure);
-            if (out.getVersion().onOrAfter(METADATA_FIELD_INTRODUCED)) {
-                out.writeMap(entry.userMetadata);
-            }
+            out.writeMap(entry.userMetadata);
             if (out.getVersion().onOrAfter(VERSION_IN_SNAPSHOT_VERSION)) {
                 Version.writeVersion(entry.version, out);
             } else {

server/src/main/java/org/elasticsearch/snapshots/SnapshotInfo.java

@@ -55,7 +55,6 @@ public final class SnapshotInfo implements Comparable<SnapshotInfo>, ToXContent,
 
     public static final String CONTEXT_MODE_PARAM = "context_mode";
     public static final String CONTEXT_MODE_SNAPSHOT = "SNAPSHOT";
-    public static final Version METADATA_FIELD_INTRODUCED = Version.V_7_3_0;
     private static final DateFormatter DATE_TIME_FORMATTER = DateFormatter.forPattern("strictDateOptionalTime");
     private static final String SNAPSHOT = "snapshot";
     private static final String UUID = "uuid";
@@ -312,11 +311,7 @@ public final class SnapshotInfo implements Comparable<SnapshotInfo>, ToXContent,
         }
         version = in.readBoolean() ? Version.readVersion(in) : null;
         includeGlobalState = in.readOptionalBoolean();
-        if (in.getVersion().onOrAfter(METADATA_FIELD_INTRODUCED)) {
-            userMetadata = in.readMap();
-        } else {
-            userMetadata = null;
-        }
+        userMetadata = in.readMap();
     }
 
     /**
@@ -714,9 +709,7 @@ public final class SnapshotInfo implements Comparable<SnapshotInfo>, ToXContent,
             out.writeBoolean(false);
         }
         out.writeOptionalBoolean(includeGlobalState);
-        if (out.getVersion().onOrAfter(METADATA_FIELD_INTRODUCED)) {
-            out.writeMap(userMetadata);
-        }
+        out.writeMap(userMetadata);
     }
 
     private static SnapshotState snapshotState(final String reason, final List<SnapshotShardFailure> shardFailures) {