Remove deprecated GetNonStableAPIKey() API

This reverts commit 5a97d03352e7dfec5c54f872eb1cb5fbe2419960.

Reason for revert: the remaining references have been removed from
internal repos and auto-rolled in crrev/c/5755818.

Original change's description:
> Partial revert of crrev/c/5741205
>
> There were still some code references outside the main Chromium repo, so re-adding the soon-to-be-deprecated API while those are migrated.
>
> Bug: 40216037, 355652328
> Change-Id: I2d30e61a5b0dfc7bb1e8031b3a1e50ee6cf975bb
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5749404
> Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
> Commit-Queue: James Lee <ljjlee@google.com>
> Cr-Commit-Position: refs/heads/main@{#1334882}

Bug: 40216037, 355652328
Change-Id: If8f2a96faabfcdf377cb1b25a83365af241ca424
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5756821
Commit-Queue: James Lee <ljjlee@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: James Lee <ljjlee@google.com>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1336626}
NOKEYCHECK=True
GitOrigin-RevId: b5c06f2580a84f9b12193cd0d514b050b5cb745b
2 files changed