Fix pg_pathman_enable_partition_router initial value

Thus it is equal to its boot value. See the commit
a73952b795632b2cf5acada8476e7cf75857e9be (Add check on initial and boot values
when loading GUCs) in PostgreSQL 16.

Author: Marina Polyakova

src/partition_router.c

@@ -63,7 +63,7 @@
 
 
 
-bool				pg_pathman_enable_partition_router = true;
+bool				pg_pathman_enable_partition_router = false;
 
 CustomScanMethods	partition_router_plan_methods;
 CustomExecMethods	partition_router_exec_methods;