Code generator makes useless include line to the binding files.

There are useless include statement in the Internals.idl,
because of generating duplicated include statements from code generator.
It is better to remove it from code generator.

BUG=263278

Review URL: https://chromiumcodereview.appspot.com/19688011

git-svn-id: svn://svn.chromium.org/blink/trunk@154890 bbb929c8-8fbe-4397-9dbb-9b2b20218538