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>

main.py

@@ -47,7 +47,7 @@ except ImportError:
 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

subcmds/list.py

@@ -15,7 +15,6 @@
 # limitations under the License.
 
 from __future__ import print_function
-import sys
 
 from command import Command, MirrorSafeCommand