[wdspec] Update invalid url for bidi fetchError tests

Using https://not_a_valid_url might cause delays on windows because it will attempt to use mDNS or DNS suffixes.
Using a fully qualified URL avoids the additional delay.

Differential Revision: https://phabricator.services.mozilla.com/D199508

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1873880
gecko-commit: 830d3304af3d78f547220a46c767f2a8cd3e4aa9
gecko-reviewers: webdriver-reviewers, Sasha

Author: juliandescottes

webdriver/tests/bidi/network/__init__.py

@@ -309,7 +309,7 @@ def assert_response_event(
 PAGE_EMPTY_SCRIPT = "/webdriver/tests/bidi/network/support/empty.js"
 PAGE_EMPTY_SVG = "/webdriver/tests/bidi/network/support/empty.svg"
 PAGE_EMPTY_TEXT = "/webdriver/tests/bidi/network/support/empty.txt"
-PAGE_INVALID_URL = "https://not_a_valid_url/"
+PAGE_INVALID_URL = "https://not_a_valid_url.test/"
 PAGE_OTHER_TEXT = "/webdriver/tests/bidi/network/support/other.txt"
 PAGE_REDIRECT_HTTP_EQUIV = (
     "/webdriver/tests/bidi/network/support/redirect_http_equiv.html"