[wptrunner] Don't honor per-request timeout for now

[jonathan-j-lee]

This is a partial revert of #46869. Using a nondefault timeout fails with:

  ▶ ERROR [expected OK] external/wpt/IndexedDB/idbindex-query-exception-order.html
  └   → WebDriverRun.run_func didn't set a result

Exception in thread Thread-4:
Traceback (most recent call last):
  File "/tmp/wpt/tools/webdriver/webdriver/transport.py", line 259, in _request
    previous_timeout = self._conn.gettimeout()
AttributeError: 'HTTPConnection' object has no attribute 'gettimeout'

... because {get,set}timeout are methods on socket.socket, not http.client.HTTP(S)Connection.