Remove complexity warning

By removing some code we have snuck the complexity level of this code
within the limit of 10, so it passes `ruff` now

app/main/views/sign_in.py

@@ -25,7 +25,7 @@
 @main.route("/sign-in", methods=(["GET", "POST"]))
 @hide_from_search_engines
 @redirect_if_logged_in
-def sign_in():  # noqa: C901
+def sign_in():
     redirect_url = request.args.get("next")
 
     form = LoginForm()