Adds missing dep to testing/scripts/run_android_wpt.pydeps

Public CQ does not check android only scripts for pydeps thus a cl
(crrev.com/c/2218528) was landed that did not change pydeps but only
broke downstream CQ.

TBR=lpz@chromium.org

Change-Id: I77c58cfb6548278366fc89a3c63220416bd25aeb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2228362Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Commit-Queue: Mohamed Heikal <mheikal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774827}

testing/scripts/run_android_wpt.pydeps

@@ -6,6 +6,7 @@
 //build/android/pylib/constants/host_paths.py
 //testing/scripts/common.py
 //testing/scripts/run_android_wpt.py
+//testing/scripts/wpt_common.py
 //testing/test_env.py
 //testing/xvfb.py
 //third_party/catapult/common/py_utils/py_utils/__init__.py