Fix override for discover api endpoint

The internals override for the discover api endpoint was
overriding the wrong variable.

Change-Id: Ic38fc57c08d0dc5478479a02c9970e74bedd8da5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3863989


Commit-Queue: Ian Wells <iwells@chromium.org>
Reviewed-by: Ian Wells <iwells@chromium.org>
Auto-Submit: Dan H <harringtond@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1041133}