pg_upgrade: Remove PGPORT handling from test suite

This code was left over from when pg_upgrade paid attention to PGPORT.
Now it would only affects the regression test run before the test run of
pg_upgrade.  You can still set PGPORT for that, but there is no reason
to have the test driver default it to 50432.

contrib/pg_upgrade/test.sh

@@ -12,8 +12,6 @@
 set -e
 
 : ${MAKE=make}
-: ${PGPORT=50432}
-export PGPORT
 
 testhost=`uname -s`