[MacOS][Signing] Revert overwriting Alerts helper app id.

Upstream fully transitioned now to helper (Alerts) and removed XPC
notification service. We should no longer mess with the identifier for
that executable.

See original change: #8755

See upstream: https://bugs.chromium.org/p/chromium/issues/detail?id=1170731

script/signing_helper.py

@@ -124,11 +124,6 @@ def AddBravePartsForSigning(parts, config):
     parts['helper-app'].options = (CodeSignOptions.RESTRICT
                                    + CodeSignOptions.KILL
                                    + CodeSignOptions.HARDENED_RUNTIME)
-    # Alerts helper is not being distributed with Chrome yet and, because it
-    # uses the same identifier as the current Alerts service, the signing fails.
-    # For now we can set a different identifier and then remove this change once
-    # the helper starts being bundled into the distribution.
-    parts['helper-alerts'].identifier = '{}.helper.alerts'.format(config.base_bundle_id)
 
     return parts