fix: remove future import

Author: ViRb3

sign.py

@@ -1,8 +1,5 @@
 #!/usr/bin/env python3
 
-# https://mypy.readthedocs.io/en/stable/runtime_troubles.html#using-classes-that-are-generic-in-stubs-but-not-at-runtime
-from __future__ import annotations
-
 import copy
 import os
 import re