Remove WM shell unit tests from WM root

We previously didn't execute WM shell unit tests on WM changes, and don't need to start now (e.g. from CL running old config ag/34645752)

Bug: 311643481
Test: N/A
Flag: TEST_ONLY
Change-Id: Ie169189f0e2c4c44f2d28694da6e16b6c36be684