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/git_command.py b/git_command.py
index 2e4974f..0e25639 100644
--- a/git_command.py
+++ b/git_command.py
@@ -58,7 +58,7 @@
 logger = RepoLogger(__file__)
 
 
-class _GitCall(object):
+class _GitCall:
     @functools.lru_cache(maxsize=None)
     def version_tuple(self):
         ret = Wrapper().ParseGitVersion()
@@ -148,7 +148,7 @@
     return path
 
 
-class UserAgent(object):
+class UserAgent:
     """Mange User-Agent settings when talking to external services
 
     We follow the style as documented here:
@@ -272,7 +272,7 @@
     return env
 
 
-class GitCommand(object):
+class GitCommand:
     """Wrapper around a single git invocation."""
 
     def __init__(