Update a FIXME notice

The bug number is wrong and I can't find the right one, d'oh.
We could *probably* safely remove this right now but I'm not
100% sure, I think it should be fine when F38 is EOL.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

tests/upgrade_run.pm

@@ -15,7 +15,7 @@ sub run {
     repo_setup();
     my $params = "-y --releasever=${relnum}";
     if ($relnum > 38) {
-        # FIXME https://bugzilla.redhat.com/show_bug.cgi?id=2230720
+        # FIXME can probably be removed when F38 goes EOL
         $params .= " --nogpgcheck --disablerepo=*modular*";
     }