Fix GetWALAvailability function code comments for WALAVAIL_REMOVED return value

When Who What
2023-01-19 23:41:49 Tom Lane (tgl) Closed in commitfest 2023-01 with status: Committed
2023-01-19 23:41:49 Tom Lane (tgl) Changed committer to tgl
2022-12-01 06:49:40 Michael Paquier (michael-kun) Closed in commitfest 2022-11 with status: Moved to next CF
2022-11-21 06:58:51 sirisha chamarthi (sirishac) Changed authors to sirisha chamarthi (sirishac)
2022-10-27 16:54:31 sirisha chamarthi (sirishac) Changed targetversion to None
2022-10-27 16:52:50 sirisha chamarthi (sirishac) Changed targetversion to 16
2022-10-27 16:51:53 sirisha chamarthi (sirishac) Attached mail thread CAKrAKeXt-=bgm=d+EDmcC9kWoikp8kbVb3LH0K3K+AGGsykpHQ@mail.gmail.com
2022-10-27 16:51:53 sirisha chamarthi (sirishac) Created patch record