Remove unused imports in depot_tools/*.py

I know that sometimes imports can have side-effects,
so unused imports shouldn't always be removed, but these
ones look like they could be.

Change-Id: Iea9f82afa99b0ea35f29a28f20ce0493b579cfee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1819860
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>

ninjalog_uploader.py

@@ -23,7 +23,6 @@ import logging
 import multiprocessing
 import os
 import platform
-import socket
 import subprocess
 import sys
 import time