CSSOM: Remove TODOs for implementing [LegacyArrayClass] on interfaces

https://github.com/w3c/csswg-drafts/issues/2601 removed
[LegacyArrayClass] from the spec, so these TODOs are no longer needed.

Change-Id: I38e6c2b0cd726d3f8af75e1c3966f794d4487af5
Reviewed-on: https://chromium-review.googlesource.com/1025313Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Commit-Queue: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553042}

third_party/blink/renderer/core/css/css_rule_list.idl

@@ -25,7 +25,6 @@
 
 // https://drafts.csswg.org/cssom/#the-cssrulelist-interface
 
-// TODO(foolip): CSSRuleList should be an [ArrayClass].
 [
     Exposed=Window
 ] interface CSSRuleList {

third_party/blink/renderer/core/css/media_list.idl

@@ -25,7 +25,6 @@
 
 // https://drafts.csswg.org/cssom/#the-medialist-interface
 
-// TODO(foolip): MediaList should be an [ArrayClass].
 [
     Exposed=Window
 ] interface MediaList {

third_party/blink/renderer/core/css/style_sheet_list.idl

@@ -20,7 +20,6 @@
 
 // https://drafts.csswg.org/cssom/#the-stylesheetlist-interface
 
-// TODO(foolip): StyleSheetList should be an [ArrayClass].
 [
     RaisesException=Constructor,
     Constructor(sequence<CSSStyleSheet> sheets),