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_superproject.py b/git_superproject.py
index 5d8c0d4..651b6db 100644
--- a/git_superproject.py
+++ b/git_superproject.py
@@ -66,7 +66,7 @@
     fatal: bool
 
 
-class Superproject(object):
+class Superproject:
     """Get commit ids from superproject.
 
     Initializes a local copy of a superproject for the manifest. This allows