Update TODO(s) in SVGTransform.idl

Update SVGMatrix vs. DOMMatrix{,ReadOnly} references to match
https://svgwg.org/svg2-draft/coords.html#InterfaceSVGTransform.

TBR=foolip@chromium.org

Review-Url: https://codereview.chromium.org/2599753002
Cr-Commit-Position: refs/heads/master@{#440400}
1 file changed