Fix outdated references to guc.c
Commit
0a20ff54f split out the GUC variables from guc.c into a new file
guc_tables.c. This updates comments referencing guc.c regarding variables
which are now in guc_tables.c.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/
6B50C70C-8C1F-4F9A-A7C0-
EEAFCC032406@yesql.se