Update reference documentation for IndexOperations.

Make sure the reference documentation is in line with available methods. Update signatures and remove no longer supported ones.

Closes: #4587

Author: christophstrobl

Diff for: src/main/antora/modules/ROOT/pages/mongodb/template-collection-management.adoc

@@ -15,16 +15,14 @@ Imperative::
 ----
 public interface IndexOperations {
 
-    void ensureIndex(IndexDefinition indexDefinition);
+    String ensureIndex(IndexDefinition indexDefinition);
 
-    void alterIndex(String name);
+    void alterIndex(String name, IndexOptions options);
 
     void dropIndex(String name);
 
     void dropAllIndexes();
 
-    void resetIndexCache();
-
     List<IndexInfo> getIndexInfo();
 }
 ----