Revert "Handle policy fetch error during force install/update."

This reverts commit 20270bf88e16a7ebd270702fe1c3d82d568b9257.

Reason for revert: http://crbug.com/399133255

Original change's description:
> Handle policy fetch error during force install/update.
>
> Roughly speaking, with this CL, all non-self-updates/installs are blocked if policies can't be obtained.
>
> Current implementation does not include a customized UI message for
> policy fetch error. Instead, it's just shows the generic update error
> (update fail to start) with extra code `kErrorPolicyFetchFailed`.
>
> This implementation relies on the assumption that a policy fetch
> is done before the policy value is queried.
>
> Low-Coverage-Reason: COVERAGE_UNDERREPORTED
> Bug: 382328658
> Change-Id: Ice73abd434bf5f7bc630b28401ebf50138f0d25c
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6077922
> Reviewed-by: S Ganesh <ganesh@chromium.org>
> Commit-Queue: Xiaoling Bao <xiaolingbao@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1397665}

Bug: 382328658, 399133255
Change-Id: I6a6e2cd1d56bfc3fed91817afe752deb7fd71ff3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6343756
Reviewed-by: Xiaoling Bao <xiaolingbao@chromium.org>
Reviewed-by: S Ganesh <ganesh@chromium.org>
Commit-Queue: Noah Rose Ledesma <noahrose@google.com>
Cr-Commit-Position: refs/heads/main@{#1431217}