zerver/migrations: Use python 3 syntax for typing.

zerver/migrations/0087_remove_old_scheduled_jobs.py

@@ -5,8 +5,7 @@ from django.db import migrations
 from django.db.backends.postgresql_psycopg2.schema import DatabaseSchemaEditor
 from django.db.migrations.state import StateApps
 
-def delete_old_scheduled_jobs(apps, schema_editor):
-    # type: (StateApps, DatabaseSchemaEditor) -> None
+def delete_old_scheduled_jobs(apps: StateApps, schema_editor: DatabaseSchemaEditor) -> None:
     """Delete any old scheduled jobs, to handle changes in the format of
     send_email. Ideally, we'd translate the jobs, but it's not really
     worth the development effort to save a few invitation reminders