[Seriff] Revert "Update ephemeral Guest Profile handling when policy is set."

This reverts commit 46d850ca.

Reason for revert: The newly added TestsForceEphemeralProfilesPolicy
times out on Windows.
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=AllGuestProfileTypes%2FEphemeralGuestProfilePolicyTest.TestsForceEphemeralProfilesPolicy%2F1&testType=browser_tests

Original change's description:
> Update ephemeral Guest Profile handling when policy is set.
>
> When |ForceEphemeralProfiles| is set to false, ProfileManager cannot
> overwrite the pref for ephemeral Guest profiles.
> To overcome the issue, a new |IsEphemeral| function is added to the
> ProfileManager which not only checks for the pref value, but also
> consider profile type.
>
> Bug: 1125474
> Change-Id: Ieb22c22d4ed5ac63abe0c01096e10397eb0b6531
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2584025


> Reviewed-by: Dominic Battré <battre@chromium.org>
> Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
> Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#840017}

TBR=battre@chromium.org,msarda@chromium.org,rhalavati@chromium.org,chromium-scoped@luci-project-accounts.iam.gserviceaccount.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1125474
Change-Id: Ifcd0bfe22022db12e0d042ec734573256a59de1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2605358


Reviewed-by: K. Moon <kmoon@chromium.org>
Reviewed-by: Sahel Sharify <sahel@chromium.org>
Commit-Queue: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840233}