Use the vote action to vote featured proposals

The action and the views were almost identical, with the supports
progress and the HTML classes of the success message element being the
only exceptions; we can use CSS for the styles instead.

app/components/proposals/votes_component.rb

@@ -1,9 +1,13 @@
 class Proposals::VotesComponent < ApplicationComponent
-  attr_reader :proposal, :vote_url
+  attr_reader :proposal
   delegate :current_user, :link_to_verify_account, :user_signed_in?, to: :helpers
 
-  def initialize(proposal, vote_url:)
+  def initialize(proposal, vote_url: nil)
     @proposal = proposal
     @vote_url = vote_url
   end
+
+  def vote_url
+    @vote_url || vote_proposal_path(proposal, value: "yes")
+  end
 end