ref: unify signature of Webhook.__call__ (#74904)

<!-- Describe your PR here. -->

Author: asottile-sentry

src/sentry_plugins/github/webhooks/events/__init__.py

@@ -1,5 +1,5 @@
 class Webhook:
-    def __call__(self, event, organization=None):
+    def __call__(self, event, organization):
         raise NotImplementedError
 
 

src/sentry_plugins/github/webhooks/events/installation.py

@@ -7,7 +7,7 @@
 
 class InstallationEventWebhook(Webhook):
     # https://developer.github.com/v3/activity/events/types/#installationevent
-    def __call__(self, event, organization=None):
+    def __call__(self, event, organization):
         action = event["action"]
         installation = event["installation"]
         # TODO(jess): handle uninstalls

src/sentry_plugins/github/webhooks/events/installation_repository.py

@@ -7,7 +7,7 @@
 
 class InstallationRepositoryEventWebhook(Webhook):
     # https://developer.github.com/v3/activity/events/types/#installationrepositoriesevent
-    def __call__(self, event, organization=None):
+    def __call__(self, event, organization):
         installation = event["installation"]
 
         integration = integration_service.get_integration(