Remove unused prototype

Commit 6f56b41 removed function get_pg_database_relfilenode but left
its prototype in place.  Remove it.

Author: alvherre

src/bin/pg_upgrade/pg_upgrade.h

@@ -396,7 +396,6 @@ void		get_sock_dir(ClusterInfo *cluster, bool live_check);
 
 /* relfilenode.c */
 
-void		get_pg_database_relfilenode(ClusterInfo *cluster);
 void transfer_all_new_tablespaces(DbInfoArr *old_db_arr,
 				  DbInfoArr *new_db_arr, char *old_pgdata, char *new_pgdata);
 void transfer_all_new_dbs(DbInfoArr *old_db_arr,