posts: fix mis-sized upvote icon in advanced tooltips.

Passing a class to svg_icon_tag accidentally overrode the other classes
we tried to set.

app/helpers/icon_helper.rb

@@ -4,8 +4,9 @@ module IconHelper
     tag.i(class: "icon #{icon_class} #{klass}", **options)
   end
 
-  def svg_icon_tag(type, path, **options)
-    tag.svg(class: "icon svg-icon #{type}", role: "img", xmlns: "http://www.w3.org/2000/svg", viewBox: "0 0 448 512", **options) do
+  def svg_icon_tag(type, path, class: nil, **options)
+    klass = binding.local_variable_get(:class)
+    tag.svg(class: "icon svg-icon #{type} #{klass}", role: "img", xmlns: "http://www.w3.org/2000/svg", viewBox: "0 0 448 512", **options) do
       tag.path(fill: "currentColor", d: path)
     end
   end

app/views/posts/show.html+tooltip.erb

@@ -8,7 +8,7 @@
 
   <span class="post-tooltip-score post-tooltip-info">
     <span><%= @post.score %></span>
-    <%= upvote_icon(class: "fa-xs") %>
+    <%= upvote_icon %>
   </span>
 
   <% if @post.last_commented_at.present? %>