product/ERP5/bin/zopewsgi.py: Silence Server and Via response headers.

In our use, waitress is embedded in Zope and not as a proxy, so it has no
legitimacy emitting Via headers.
While this process often is the origin server, Server response header is
optional and should be left to the lower layers to control, and not
auto-generated by waitress.

product/ERP5/bin/zopewsgi.py

@@ -187,4 +187,6 @@ def runwsgi():
         logger=logging.getLogger("access"),
         threads=conf.zserver_threads,
         asyncore_use_poll=True,
+        # Prevent waitress from adding its own Via and Server response headers.
+        ident=None,
     ).run()