Replace closet_hangers/petpage.js with modern CSS

We use jQuery to basically simulate the `:has()` pseudoselector. Let's
just, use `:has()` now!

app/assets/javascripts/closet_hangers/petpage.js

@@ -1,8 +0,0 @@
-(function () {
-	function setChecked() {
-		var el = $(this);
-		el.closest("li").toggleClass("checked", el.is(":checked"));
-	}
-
-	$("#petpage-closet-lists input").click(setChecked).each(setChecked);
-})();

app/assets/stylesheets/closet_hangers/petpage.sass

@@ -38,7 +38,7 @@
       label
         padding: .25em .75em .25em .25em
 
-      &.checked
+      &:has(:checked)
         background: $module-bg-color
         border-radius: 3px
         border: 1px solid $module-border-color

app/views/closet_hangers/petpage.html.haml

@@ -29,7 +29,5 @@
     :lists_by_owned => @visible_closet_lists_by_owned,
     :unlisted_hangers_by_owned => @visible_unlisted_closet_hangers_by_owned)
 
-- content_for :javascripts_body do
-  = javascript_include_tag 'jquery', 'closet_hangers/petpage'
 - content_for :stylesheets do
   = stylesheet_link_tag 'closet_hangers/petpage'