This reverts commit 724dbeba.

Reason for revert: bots remain red after revert.

Original change's description:
> Revert "Fixing libyuv gn check."
> 
> This reverts commit b625f7b9.
> 
> Reason for revert: ios builds broke shortly after this CL, so trying a revert to get builds back to green.
> 
> Original change's description:
> > Fixing libyuv gn check.
> > 
> > Starting from [1], GN is able to ensure that the inclusion or headers
> > with relative paths is matched by a GN dependency.
> > 
> > This CL fixes the libyuv build graph according to GN.
> > 
> > [1] - https://chromium-review.googlesource.com/c/chromium/src/+/827014
> > 
> > Bug: webrtc:8850
> > Change-Id: I7e0f9a8bd1ae2d205213dc75bf322be587efd1f5
> > Reviewed-on: https://chromium-review.googlesource.com/903843
> > Reviewed-by: Frank Barchard <fbarchard@chromium.org>
> > Commit-Queue: Frank Barchard <fbarchard@chromium.org>
> 
> TBR=fbarchard@chromium.org,mbonadei@chromium.org
> 
> # Not skipping CQ checks because original CL landed > 1 day ago.
> 
> Bug: webrtc:8850
> Change-Id: I8585de252bd83e2c628a37b0a0d5324ed961209e
> Reviewed-on: https://chromium-review.googlesource.com/912178
> Reviewed-by: Frank Barchard <fbarchard@chromium.org>
> Commit-Queue: Frank Barchard <fbarchard@chromium.org>

TBR=fbarchard@chromium.org,mbonadei@chromium.org

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

Bug: webrtc:8850
Change-Id: Idfd37e0e20d278b374c57d7e2c5465971aae3a52
Reviewed-on: https://chromium-review.googlesource.com/914529Reviewed-by: Frank Barchard <fbarchard@chromium.org>