Switch off parallel workers because of

danolivo · Andrey Lepikhov · commit a936846d0beb · 2021-06-15T11:35:24.000+05:00
unsteadiness. Change variable and remove comment. Induced by a test passing
 problem on the powerpc node of the buildfarm.
diff --git a/conf.add b/conf.add
@@ -1,3 +1,3 @@
 autovacuum = off
 shared_preload_libraries = 'postgres_fdw, aqo'
-max_parallel_workers = 0 # switch off parallel workers because of unsteadiness
+max_parallel_workers_per_gather = 0
