Don't link to specific WHATWG multipage page

"Links to the multipage version of the specification are unfortunately
likely to break over time."
-- https://html.spec.whatwg.org/multipage/asefij.html

This commit removes all references to the specific pages when viewing
WHATWG using multipage mode. I went through all these links and they
redirect fine.

Regex used to generate this commit:

`s_whatwg.org/multipage/.*#_whatwg.org/multipage/#_g`

components/script/dom/worker.rs

@@ -35,7 +35,7 @@ use std::sync::mpsc::{channel, Sender};
 
 pub type TrustedWorkerAddress = Trusted<Worker>;
 
-// https://html.spec.whatwg.org/multipage/workers.html#worker
+// https://html.spec.whatwg.org/multipage/#worker
 #[dom_struct]
 pub struct Worker {
     eventtarget: EventTarget,