Clean up a few instances of "MetaData"

We recently cleaned up the use of the word "metadata" across the
codebase. A few additional uses have trickled in, likely from
in-progress work. This commit cleans up these last few instances.

Relates #54519

server/src/main/java/org/elasticsearch/action/admin/indices/datastream/CreateDataStreamAction.java

@@ -125,9 +125,9 @@ public class CreateDataStreamAction extends ActionType<AcknowledgedResponse> {
         @Inject
         public TransportAction(TransportService transportService, ClusterService clusterService, ThreadPool threadPool,
                                ActionFilters actionFilters, IndexNameExpressionResolver indexNameExpressionResolver,
-                               MetadataCreateIndexService metaDataCreateIndexService) {
+                               MetadataCreateIndexService metadataCreateIndexService) {
             super(NAME, transportService, clusterService, threadPool, actionFilters, Request::new, indexNameExpressionResolver);
-            this.metadataCreateIndexService = metaDataCreateIndexService;
+            this.metadataCreateIndexService = metadataCreateIndexService;
         }
 
         @Override

server/src/test/java/org/elasticsearch/search/aggregations/pipeline/InternalPercentilesBucketTests.java

@@ -46,17 +46,17 @@ import static org.hamcrest.Matchers.equalTo;
 public class InternalPercentilesBucketTests extends InternalAggregationTestCase<InternalPercentilesBucket> {
 
     @Override
-    protected InternalPercentilesBucket createTestInstance(String name, Map<String, Object> metaData) {
-        return createTestInstance(name, metaData, randomPercents(), true);
+    protected InternalPercentilesBucket createTestInstance(String name, Map<String, Object> metadata) {
+        return createTestInstance(name, metadata, randomPercents(), true);
     }
 
-    private static InternalPercentilesBucket createTestInstance(String name, Map<String, Object> metaData,
+    private static InternalPercentilesBucket createTestInstance(String name, Map<String, Object> metadata,
             double[] percents, boolean keyed) {
         final double[] percentiles = new double[percents.length];
         for (int i = 0; i < percents.length; ++i) {
             percentiles[i] = frequently() ? randomDouble() : Double.NaN;
         }
-        return createTestInstance(name, metaData, percents, percentiles, keyed);
+        return createTestInstance(name, metadata, percents, percentiles, keyed);
     }
 
     private static InternalPercentilesBucket createTestInstance(String name, Map<String, Object> metadata,

test/framework/src/main/java/org/elasticsearch/test/InternalAggregationTestCase.java

@@ -353,8 +353,8 @@ public abstract class InternalAggregationTestCase<T extends InternalAggregation>
     /** Return an instance on an unmapped field. */
     protected final T createUnmappedInstance(String name) {
         Map<String, Object> metadata = new HashMap<>();
-        int metaDataCount = randomBoolean() ? 0 : between(1, 10);
-        while (metadata.size() < metaDataCount) {
+        int metadataCount = randomBoolean() ? 0 : between(1, 10);
+        while (metadata.size() < metadataCount) {
             metadata.put(randomAlphaOfLength(5), randomAlphaOfLength(5));
         }
         return createUnmappedInstance(name, metadata);