Remove use_c10_dispatcher: full lines

Pull Request resolved: #49259

Since `use_c10_dispatcher: full` is now the default, we can remove all those pesky lines mentioning it. Only the `use_c10_dispatcher: hacky_wrapper_for_legacy_signatures` lines are left.
ghstack-source-id: 118710662

Differential Revision: [D25506526](https://our.internmc.facebook.com/intern/diff/D25506526/)