[SVG] Remove SVGResourcesCache::clientStyleChanged() deadcode.

The method is only ever called for RenderSVG* objects, there is no need
to handle the !renderer->node()->isSVGElement() case.

R=schenney@chromium.org,pdr@chromium.org

Review URL: https://codereview.chromium.org/26235004

git-svn-id: svn://svn.chromium.org/blink/trunk@159034 bbb929c8-8fbe-4397-9dbb-9b2b20218538