The parser already changes all negative equality comparison operations
to their positive pendants in {ParserBase::ParseBinaryExpression}. No
other source of the Token::NE exists in the system. We can remove all
handling from the compiler and interpreter backends.

R=bmeurer@chromium.org

Change-Id: I58722c08dd8e498f20c65886fce86b8172737b10
Reviewed-on: https://chromium-review.googlesource.com/449716Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43627}