Rename pending_list_cleanup_size to gin_pending_list_limit.

Since this parameter is only for GIN index, it's better to
add "gin" to the parameter name for easier understanding.

src/backend/utils/misc/guc.c

@@ -2543,12 +2543,12 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"pending_list_cleanup_size", PGC_USERSET, CLIENT_CONN_STATEMENT,
+		{"gin_pending_list_limit", PGC_USERSET, CLIENT_CONN_STATEMENT,
 			gettext_noop("Sets the maximum size of the pending list for GIN index."),
 			 NULL,
 			GUC_UNIT_KB
 		},
-		&pending_list_cleanup_size,
+		&gin_pending_list_limit,
 		4096, 64, MAX_KILOBYTES,
 		NULL, NULL, NULL
 	},

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

@@ -519,7 +519,7 @@
 #bytea_output = 'hex'			# hex, escape
 #xmlbinary = 'base64'
 #xmloption = 'content'
-#pending_list_cleanup_size = 4MB
+#gin_pending_list_limit = 4MB
 
 # - Locale and Formatting -