Update API comments for mutable tiering options (#13642)

Summary:
Mutable as described in 9.11 release notes

Pull Request resolved: #13642

Test Plan: already tested in tiered_compaction_test; search for ApplyConfigChange

Reviewed By: jowlyzhang

Differential Revision: D75458238

Pulled By: pdillinger

fbshipit-source-id: a2aa7273dbdc7be95aceed76edf502f883130172

Author: pdillinger

include/rocksdb/advanced_options.h

@@ -863,7 +863,7 @@ struct AdvancedColumnFamilyOptions {
   //
   // Default: 0 (disable the feature)
   //
-  // Not dynamically changeable, change it requires db restart.
+  // Dynamically changeable through the SetOptions() API
   uint64_t preclude_last_level_data_seconds = 0;
 
   // EXPERIMENTAL
@@ -886,7 +886,7 @@ struct AdvancedColumnFamilyOptions {
   //
   // Default: 0 (disable the feature)
   //
-  // Not dynamically changeable, change it requires db restart.
+  // Dynamically changeable through the SetOptions() API
   uint64_t preserve_internal_time_seconds = 0;
 
   // When set, large values (blobs) are written to separate blob files, and