Remove redundant url clones

They are now redundant since now document.url() returns a struct rather
than a reference.

components/script/dom/htmllinkelement.rs

@@ -280,9 +280,9 @@ impl HTMLLinkElement {
             destination: Destination::Style,
             credentials_mode: CredentialsMode::Include,
             use_url_credentials: true,
-            origin: document.url().clone(),
+            origin: document.url(),
             pipeline_id: Some(self.global().pipeline_id()),
-            referrer_url: Some(document.url().clone()),
+            referrer_url: Some(document.url()),
             referrer_policy: referrer_policy,
             .. RequestInit::default()
         };