Revert "Change Picture: Policy to disable user avatar videos"

This reverts commit 0235aec2ea6e780e2712a45b6d31156a64a0b370.

Reason for revert: Accidentally disabled motion stills by default
and not clear if we want to add this policy or not.

Original change's description:
> Change Picture: Policy to disable user avatar videos
> 
> Adds a policy to control whether recording of videos for user
> avatar should be allowed.
> 
> Bug: 763735
> Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
> Change-Id: I30ba35f867533acb7431914b7eea7e9bf443b36b
> Reviewed-on: https://chromium-review.googlesource.com/704199
> Commit-Queue: David Reveman <reveman@chromium.org>
> Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
> Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#507891}

TBR=stevenjb@chromium.org,reveman@chromium.org,emaxx@chromium.org

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

Bug: 763735
Change-Id: I8b1c14259c563593854e28ac82c5bf4ee2e9597b
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Reviewed-on: https://chromium-review.googlesource.com/716343
Reviewed-by: David Reveman <reveman@chromium.org>
Commit-Queue: David Reveman <reveman@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#508594}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 0ab69aae8867b2ed55c6634acae3c0519e58ca38