Address PR comments

- Remove fn `url_is_local`
- Remove fn `set_local_urls_only`
- Fix `test_fetch_with_local_urls_only`

components/net_traits/request.rs

@@ -257,8 +257,4 @@ impl Request {
             _ => false
         }
     }
-
-    pub fn set_local_urls_only(&mut self, local_urls_only: bool) {
-        self.local_urls_only = local_urls_only;
-    }
 }