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>

progress.py

@@ -82,7 +82,7 @@ def jobs_str(total):
     return f"{total} job{'s' if total > 1 else ''}"
 
 
-class Progress(object):
+class Progress:
     def __init__(
         self,
         title,