Drop RenderStyle-arg. from RenderSVGResource{Filter,Masker}::prepareEffect

It's unused in both cases.

BUG=420022

Review URL: https://codereview.chromium.org/674373004

git-svn-id: svn://svn.chromium.org/blink/trunk@184457 bbb929c8-8fbe-4397-9dbb-9b2b20218538