Move shares/modal body class to layout (#31789)

app/controllers/shares_controller.rb

@@ -4,13 +4,6 @@ class SharesController < ApplicationController
   layout 'modal'
 
   before_action :authenticate_user!
-  before_action :set_body_classes
 
   def show; end
-
-  private
-
-  def set_body_classes
-    @body_classes = 'modal-layout compose-standalone'
-  end
 end

app/views/layouts/modal.html.haml

@@ -1,6 +1,8 @@
 - content_for :header_tags do
   = javascript_pack_tag 'public', crossorigin: 'anonymous'
 
+- content_for :body_classes, 'modal-layout compose-standalone'
+
 - content_for :content do
   - if user_signed_in? && !@hide_header
     .account-header