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'
```

1 files changed, 3 insertions, 3 deletions

diff --git a/components/script/dom/htmlcollection.rs b/components/script/dom/htmlcollection.rs
index a2cf605bc7e..a6871bf107f 100644
--- a/components/script/dom/htmlcollection.rs
+++ b/components/script/dom/htmlcollection.rs
@@ -175,7 +175,7 @@ impl HTMLCollection {
 }
 
 impl<'a> HTMLCollectionMethods for JSRef<'a, HTMLCollection> {
-    // http://dom.spec.whatwg.org/#dom-htmlcollection-length
+    // https://dom.spec.whatwg.org/#dom-htmlcollection-length
     fn Length(self) -> u32 {
         match self.collection {
             CollectionTypeId::Static(ref elems) => elems.len() as u32,
@@ -188,7 +188,7 @@ impl<'a> HTMLCollectionMethods for JSRef<'a, HTMLCollection> {
         }
     }
 
-    // http://dom.spec.whatwg.org/#dom-htmlcollection-item
+    // https://dom.spec.whatwg.org/#dom-htmlcollection-item
     fn Item(self, index: u32) -> Option<Temporary<Element>> {
         let index = index as usize;
         match self.collection {
@@ -205,7 +205,7 @@ impl<'a> HTMLCollectionMethods for JSRef<'a, HTMLCollection> {
         }
     }
 
-    // http://dom.spec.whatwg.org/#dom-htmlcollection-nameditem
+    // https://dom.spec.whatwg.org/#dom-htmlcollection-nameditem
     fn NamedItem(self, key: DOMString) -> Option<Temporary<Element>> {
         // Step 1.
         if key.is_empty() {