Fix typo in Makefile for installcheck-resgroup target
Fix typo in Makefile for installcheck-resgroup target

The --load-extension option was misspelt as load_extension.  Resource group
tests are difficult to run locally, neither are they run in PR pipeline.  That
makes it difficult to catch such errors.

50wu/gpdb,xinzweb/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,adam8157/gpdb,50wu/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,xinzweb/gpdb,50wu/gpdb,50wu/gpdb,ashwinstar/gpdb,xinzweb/gpdb,xinzweb/gpdb,xinzweb/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,lisakowen/gpdb,lisakowen/gpdb,adam8157/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,adam8157/gpdb,adam8157/gpdb,jmcatamney/gpdb,lisakowen/gpdb,lisakowen/gpdb,50wu/gpdb,adam8157/gpdb,lisakowen/gpdb,adam8157/gpdb,greenplum-db/gpdb,xinzweb/gpdb,xinzweb/gpdb,lisakowen/gpdb,ashwinstar/gpdb,lisakowen/gpdb,ashwinstar/gpdb,lisakowen/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,50wu/gpdb,50wu/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,xinzweb/gpdb,greenplum-db/gpdb,ashwinstar/gpdb