Delete unused WebSettings method

This deletes WebSettings::setUseExpandedHeuristicsForGpuRasterization
which no longer has any callers.

BUG=404866

Review URL: https://codereview.chromium.org/500163003

git-svn-id: svn://svn.chromium.org/blink/trunk@181251 bbb929c8-8fbe-4397-9dbb-9b2b20218538