Update WHATWG links to use HTTPS

Extracted this out of #5649

This commit was created with the following commands:

```
find . -iname "*.webidl" -type f -print0 | xargs -0 sed -i '' 's/http:\(.*\)whatwg.org/https:\1whatwg.org/g'
```

```
find . -iname "*.rs" -type f -print0 | xargs -0 sed -i '' 's/http:\(.*\)whatwg.org/https:\1whatwg.org/g'
```

components/script/dom/bindings/codegen/test/TestDictionary.webidl

@@ -6,4 +6,4 @@
 
 dictionary GrandparentDict {
   double someNum;
-};
+};