clean up shebang of manage.py (#271)

Reviewed-on: Fediversity/Fediversity#271
Reviewed-by: Valentin Gagarin <valentin.gagarin@tweag.io>
Co-authored-by: Kiara Grouwstra <kiara@procolix.eu>
Co-committed-by: Kiara Grouwstra <kiara@procolix.eu>

panel/src/manage.py

@@ -1,4 +1,4 @@
-#!/nix/store/px2nj16i5gc3d4mnw5l1nclfdxhry61p-python3-3.12.7/bin/python
+#!/usr/bin/env python
 """Django's command-line utility for administrative tasks."""
 import os
 import sys