Remove comment about renamed member in URLUtils.idl

Per comment of arv@ in:
https://codereview.chromium.org/225263003/#msg12
query was renamed searchParams.

TBR=arv

Review URL: https://codereview.chromium.org/229663003

git-svn-id: svn://svn.chromium.org/blink/trunk@171110 bbb929c8-8fbe-4397-9dbb-9b2b20218538