Remove the query_id_squash_values GUC

Commit 62d712ecfd introduced the capability to calculate the same
queryId for queries with different lengths of constants in a list for an
IN clause.  This behavior was originally enabled with a GUC
query_id_squash_values.  After a discussion about the value of such a
GUC, it was decided to back out of the use of a GUC and make the
squashing behavior the only available option.

Author: Sami Imseih <samimseih@gmail.com>
Discussion: https://postgr.es/m/Z-LZyygkkNyA8-kR@msg.df7cb.de
Discussion: https://postgr.es/m/CA+q6zcVTK-3C-8NWV1oY2NZrvtnMCDqnyYYyk1T7WMUG65MeOQ@mail.gmail.com

src/backend/utils/misc/guc_tables.c

@@ -2122,16 +2122,6 @@ struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
-	{
-		{"query_id_squash_values", PGC_USERSET, STATS_MONITORING,
-			gettext_noop("Allows to merge constants in a list when computing "
-						 "query_id."),
-		},
-		&query_id_squash_values,
-		false,
-		NULL, NULL, NULL
-	},
-
 	{
 		{"vacuum_truncate", PGC_USERSET, VACUUM_DEFAULT,
 			gettext_noop("Enables vacuum to truncate empty pages at the end of the table."),

src/backend/utils/misc/postgresql.conf.sample

@@ -664,7 +664,6 @@
 # - Monitoring -
 
 #compute_query_id = auto
-#query_id_squash_values = off
 #log_statement_stats = off
 #log_parser_stats = off
 #log_planner_stats = off