Обсуждение: pgsql: Adjust comments that called MultiXactIds "XMIDs".

Adjust comments that called MultiXactIds "XMIDs".

Oversights in commits 0b018fab and f3c15cbe.

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/9887dd38f9660721e4ef63333ab81a60b1b3da92

Modified Files
--------------
src/backend/access/heap/heapam.c                     | 2 +-
src/backend/commands/vacuum.c                        | 2 +-
src/test/isolation/specs/vacuum-no-cleanup-lock.spec | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)