Fix a couple of trivial issues in jsonb.c
Fix a couple of trivial issues in jsonb.c

Typo "aggreagate" appeared three times, and the return value of function
JsonbIteratorNext() was being assigned to an int variable in a bunch of
places.

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