Revert of [Android] Temporarily suppress RTL start&end check error. (patchset #1...

Revert of [Android] Temporarily suppress RTL start&end check error. (patchset #1 id:1 of https://codereview.chromium.org/445753002/)

Reason for revert:
Android SDK fixed the issue, so we can convert back from warning to error.

Original issue's description:
> [Android] Temporarily suppress RTL start&end check error.
>
> The newest Android SDK had start&end attributes in non -v17 resources.
> Temporarily change the checking script from error to warning so that
> people can continue to work before it is fixed. This should be
> reverted once the issue is addressed
>
> BUG=None
>
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=287711

TBR=newt@chromium.org,tedchoc@chromium.org,dfalcantara@chromium.org
BUG=None

Review URL: https://codereview.chromium.org/555253004

Cr-Commit-Position: refs/heads/master@{#294038}