pgsql: Remove useless casts to (const void *)

Remove useless casts to (const void *)

Similar to commit 7f798aca1d5, but I didn't think to look for "const"
as well.

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/8743ea1b2eb3dfbb024f40e8d9952cd85596f552

Modified Files
--------------
src/backend/storage/buffer/bufmgr.c            | 4 ++--
src/backend/storage/lmgr/lock.c                | 2 +-
src/bin/pg_dump/pg_backup_archiver.c           | 2 +-
src/test/modules/test_tidstore/test_tidstore.c | 4 ++--
4 files changed, 6 insertions(+), 6 deletions(-)