Remove warning from run-bindings-tests
https://bugs.webkit.org/show_bug.cgi?id=110285

Reviewed by Kentaro Hara.

Since wkrev.com/139331 run-bindings-tests has been harmlessly emitting
"Unknown option: idlattributesfile". That option was removed from
bindings/scripts/preprocess-idls.pl but was still being passed by
the test script. Remove it.

* Scripts/webkitpy/bindings/main.py:
(BindingsTests.generate_supplemental_dependency): Remove unused arg.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143425 268f45cc-cd09-0410-ab3c-d52691b4dbfc