Remove unused imports

flake8 reports:

  F401 'name' imported but unused

Change-Id: Id45d6efa87ddf53f2c4a0f0c4136ea361ab1b746
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/254592
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: David Pursehouse <dpursehouse@collab.net>
diff --git a/main.py b/main.py
index f6c93e4..b2845d8 100755
--- a/main.py
+++ b/main.py
@@ -47,7 +47,7 @@
 from color import SetDefaultColoring
 import event_log
 from repo_trace import SetTrace
-from git_command import git, GitCommand, user_agent
+from git_command import user_agent
 from git_config import init_ssh, close_ssh
 from command import InteractiveCommand
 from command import MirrorSafeCommand