remove no longer needed one-time sync command

app/__main__.py

@@ -185,23 +185,6 @@ def send_reminders() -> None:
                 session.commit()
 
 
-@app.command()
-def sync_applications_with_external_onboarding() -> None:
-    """
-    Email borrowers who have selected a lender with an external onboarding system to remind them to start the
-    onboarding process.
-
-    Use this command
-    """
-    with contextmanager(get_db)() as session:
-        for application in models.Application.pending_external_onboarding(
-            session, (models.ApplicationStatus.STARTED,)
-        ):
-            mail.send(session, aws.ses_client, models.MessageType.BORROWER_EXTERNAL_ONBOARDING_REMINDER, application)
-
-            session.commit()
-
-
 @app.command()
 def update_applications_to_lapsed() -> None:
     """Lapse applications that have been waiting for the borrower to respond for some time."""