Fix broken timeout test and re-enable

I think the root cause was double registering request handlers due to inheriting from GlicFreControllerUiTest instead of InteractiveGlicTest directly. The theory is that on the mac-arm64-rel bot the file serving handler was triggering first and failing before the timeout handler could be triggered. This CL registers just a single request handler that will hang on request.

Bug: 429040435, 427261741
Change-Id: If4e68d8ebb23ff3552952b7b92bf6f55aa9b493e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6701947
Reviewed-by: Trevor Perrier <perrier@chromium.org>
Reviewed-by: Andrea Gomez <andreaxg@google.com>
Commit-Queue: Nick Birnie <birnie@google.com>
Cr-Commit-Position: refs/heads/main@{#1481961}