Explicitly place '/' before fragment for multipage spec links

This prevents us from 301 redirecting, which could cause the fragment to
get lost

components/script/dom/htmloutputelement.rs

@@ -54,7 +54,7 @@ impl HTMLOutputElementMethods for HTMLOutputElement {
         ValidityState::new(window.r())
     }
 
-    // https://html.spec.whatwg.org/multipage#dom-fae-form
+    // https://html.spec.whatwg.org/multipage/#dom-fae-form
     fn GetForm(&self) -> Option<Root<HTMLFormElement>> {
         self.form_owner()
     }