Expand wpt lint to cover moz suite as well

[gterzian]

There is a wpt lint that checks for stuff like leaving a console.log in a test file, at
https://github.com/servo/servo/blob/510ffde3f18d02f19be1e90baa903239922a8e49/python/servo/lints/wpt_lint.py

However, it doesn't seem to work for tests added to the "mozilla" folder, see https://github.com/servo/servo/pull/23887/files#r309177019

The "mozilla" folder is at https://github.com/servo/servo/tree/510ffde3f18d02f19be1e90baa903239922a8e49/tests/wpt/mozilla/tests/mozilla

Could be an error in the python code using the wrong filepath...

[highfive]

cc @wafflespeanut

[gterzian]

A good way to check your fix is simply doing ./mach test-tidy, since we currently have a console.log checked-in, it should fail. Then you could also remove it, so that your PR would actually pass CI...