Update RocksDB submodule to 7.5.4

Upstream commit ID: facebook/mysql-5.6@3d9431c
PS-8494: Merge percona-202206 (https://jira.percona.com/browse/PS-8494)

Summary:
Following rocksdb update doc for new 8.0.28 release:

https://www.internalfb.com/intern/wiki/MySQL/MySQL_Internal_Documentation/MySQL_Internal_Developers_Guide/Mysql-development-quick-start-guide/How_to_update_RockDB_submodule/

update-submodule: rocksdb

Differential Revision: D40323103

fbshipit-source-id: 0541143dcd08c512fbb1286a2bcdf4543b8861e6

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Revert RocksDB submodule back to 7.5.fb

Upstream commit ID: facebook/mysql-5.6@f2646bb
PS-8494: Merge percona-202206 (https://jira.percona.com/browse/PS-8494)

Summary:
Reverting RocksDB back to 7.5.fb until deadlock between LockWAL() and
GetSortedWALFiles() is resolved.

update-submodule: rocksdb

Reviewed By: cenalulu

Differential Revision: D41282484

fbshipit-source-id: 033d2d966e6e1ee4871151573fd1c1abfd1f8ffe