ref: Remove the default entity from the post process forwarder (#40131)

This is no longer a good default (and should probably be eventually
deprecated all together) since errors and transactions are now being
mapped to different topics by default in Sentry and Snuba (which
prevents this from working properly). This change forces the user to
pass a value here.

src/sentry/runner/commands/run.py

@@ -349,7 +349,6 @@ def cron(**options):
 )
 @click.option(
     "--entity",
-    default="all",
     type=click.Choice(["all", "errors", "transactions"]),
     help="The type of entity to process (all, errors, transactions).",
 )