Remove extra double quote in options.h (#8550)

Summary:
There is an extra "  in options.h (`"index block""`)

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8550

Test Plan: None

Reviewed By: jay-zhuang

Differential Revision: D29746077

Pulled By: autopear

fbshipit-source-id: 2e5117296e5414b7c7440d990926bc1e567a0b4f

include/rocksdb/options.h

@@ -1390,7 +1390,7 @@ struct ReadOptions {
   // Default: true
   bool verify_checksums;
 
-  // Should the "data block"/"index block"" read for this iteration be placed in
+  // Should the "data block"/"index block" read for this iteration be placed in
   // block cache?
   // Callers may wish to set this field to false for bulk scans.
   // This would help not to the change eviction order of existing items in the