LibWeb: Remove resolved FIXME about putting HTMLALlCollection in HTML NS

This was an unfortunate artifact from development. I originally added
this class in the DOM namespace alongside HTMLCollection until I
realized it was defined by the HTML spec instead. To remind myself to
move it over to the HTML namespace, I left this comment. It was moved
to the correct namespace before upstreaming to the main repo, but I
forgot to remove this comment!

Userland/Libraries/LibWeb/HTML/HTMLAllCollection.h

@@ -15,8 +15,6 @@
 
 namespace Web::HTML {
 
-// FIXME: Should be part of HTML namespace!
-
 class HTMLAllCollection : public Bindings::PlatformObject {
     WEB_PLATFORM_OBJECT(HTMLAllCollection, Bindings::PlatformObject);
     JS_DECLARE_ALLOCATOR(HTMLAllCollection);