Revert "vp8: Real-time mode: reduce mode_check_freq thresh for speed 10."

Revert "vp8: Real-time mode: reduce mode_check_freq thresh for speed 10."

This reverts commit 4a7424adba7a65766a92635dc67b6e7d94646693.

Reason for revert: <INSERT REASONING HERE>
Possibly causing test failures in roll into chromium.

Original change's description:
> vp8: Real-time mode: reduce mode_check_freq thresh for speed 10.
>
> Reduces quality regression at speed 10 for real-time mode.
>
> Change-Id: I9f624bea9ca262dab32ce9de7d6d91175d6becc8
>

TBR=marpan@google.com,builds@webmproject.org,jianj@google.com
# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I1defcb74e78a5a3bd29b7d1b21a96a79fa26a457