Remove dead code path (typed array interfaces)

Typed arrays all have custom bindings, so code path that checks if an
interface is a typed array (IsTypedArray($interfaceName)) is dead code.

This removes it to avoid being misleading (and clarify rewrite);
no changes to generated code.

Obviously we want to remove these custom bindings, but the existing dead
code isn't helpful.

R=haraken

Review URL: https://codereview.chromium.org/129793007

git-svn-id: svn://svn.chromium.org/blink/trunk@165039 bbb929c8-8fbe-4397-9dbb-9b2b20218538