zopewsgi: fixes UnboundLocalError: local variable 'warnings' referenced before assignment

91cc6c4e (ERP5Type/Utils: configure warnings in zopewsgi, 2024-02-16)
was bad, on python2 zope did not start.

product/ERP5/bin/zopewsgi.py

@@ -253,7 +253,6 @@ def runwsgi():
       from Signals.SignalHandler import SignalHandler
       SignalHandler.registerHandler(signal.SIGTERM, sys.exit)
     else:
-      import warnings
       warnings.warn("zope4py3: SignalHandling not implemented!")
 
     if args.timerserver_interval: