Update format_version comment for 6.6.0

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/6097

Differential Revision: D18729661

Pulled By: pdillinger

fbshipit-source-id: d2e4a9d6803aad8dd61ececd5c2b861e6f2da73b

include/rocksdb/table.h

@@ -269,9 +269,9 @@ struct BlockBasedTableOptions {
   // probably use this as it would reduce the index size.
   // This option only affects newly written tables. When reading existing
   // tables, the information about version is read from the footer.
-  // 5 -- Can be read by RocksDB's versions since X.X.X (something after 6.4.6)
-  // Full and partitioned filters use a generally faster and more accurate
-  // Bloom filter implementation, with a different schema.
+  // 5 -- Can be read by RocksDB's versions since 6.6.0. Full and partitioned
+  // filters use a generally faster and more accurate Bloom filter
+  // implementation, with a different schema.
   uint32_t format_version = 2;
 
   // Store index blocks on disk in compressed format. Changing this option to