Fix function name in comment

The name of the function resulting from the macro expansion was
incorrectly stated.

Backpatch to 16 where it was introduced.

Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/20231101.172308.1740861597185391383.horikyota.ntt@gmail.com
Backpatch-through: v16

Author: danielgustafsson

src/backend/utils/adt/pgstatfuncs.c

@@ -78,7 +78,7 @@ PG_STAT_GET_RELENTRY_INT64(ins_since_vacuum)
 /* pg_stat_get_live_tuples */
 PG_STAT_GET_RELENTRY_INT64(live_tuples)
 
-/* pg_stat_get_mods_since_analyze */
+/* pg_stat_get_mod_since_analyze */
 PG_STAT_GET_RELENTRY_INT64(mod_since_analyze)
 
 /* pg_stat_get_numscans */