delete Python 2 (object) compat

Bug: 302871152
Change-Id: I39636d73a6e1d69efa8ade74f75c5381651e6dc8
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/390054
Commit-Queue: Mike Frysinger <vapier@google.com>
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Tested-by: Mike Frysinger <vapier@google.com>
diff --git a/hooks.py b/hooks.py
index 337c262..6ded08b 100644
--- a/hooks.py
+++ b/hooks.py
@@ -22,7 +22,7 @@
 from git_refs import HEAD
 
 
-class RepoHook(object):
+class RepoHook:
     """A RepoHook contains information about a script to run as a hook.
 
     Hooks are used to run a python script before running an upload (for