drop python3.6 support

python 3.6 reached end of life on 2021-12-23

Committed via https://github.com/asottile/all-repos
diff --git a/pre_commit_hooks/check_added_large_files.py b/pre_commit_hooks/check_added_large_files.py
index e1beb4e..79c8d4e 100644
--- a/pre_commit_hooks/check_added_large_files.py
+++ b/pre_commit_hooks/check_added_large_files.py
@@ -1,16 +1,16 @@
+from __future__ import annotations
+
 import argparse
 import math
 import os
 import subprocess
-from typing import Optional
 from typing import Sequence
-from typing import Set
 
 from pre_commit_hooks.util import added_files
 from pre_commit_hooks.util import zsplit
 
 
-def filter_lfs_files(filenames: Set[str]) -> None:  # pragma: no cover (lfs)
+def filter_lfs_files(filenames: set[str]) -> None:  # pragma: no cover (lfs)
     """Remove files tracked by git-lfs from the set."""
     if not filenames:
         return
@@ -54,7 +54,7 @@
     return retv
 
 
-def main(argv: Optional[Sequence[str]] = None) -> int:
+def main(argv: Sequence[str] | None = None) -> int:
     parser = argparse.ArgumentParser()
     parser.add_argument(
         'filenames', nargs='*',