Remove the -S option when invoking the bindings generator
to allow implicit 'import site' by the python runtime.

NOTRY=true
BUG=425932

Review URL: https://codereview.chromium.org/674503002

git-svn-id: svn://svn.chromium.org/blink/trunk@184195 bbb929c8-8fbe-4397-9dbb-9b2b20218538