fix bug in 1138b6754bdd: the "if" of an elif chain was moved, attaching the

elif to the previous if and breaking "once" in the process, under some
circumstances

--HG--
branch : release-pypy3.7-v7.x
2 jobs for release-pypy3.7-v7.3.6 in 28 minutes and 50 seconds (queued for 1 second)
latest
Status Name Job ID Coverage
  Test
passed check_rpython_annotations #254245

00:05:17

passed hpy_tests #254246

00:28:50