Burn check_signature dev script.

Broken on Python 3, so clearly unused.

Author: David Robertson

mypy.ini

@@ -24,7 +24,6 @@ files =
 exclude = (?x)
   ^(
    |scripts-dev/build_debian_packages.py
-   |scripts-dev/check_signature.py
    |scripts-dev/definitions.py
    |scripts-dev/federation_client.py
    |scripts-dev/hash_history.py