Fix layout of identity proofs settings (mastodon#11126)

Author: acid-chicken

app/controllers/settings/identity_proofs_controller.rb

@@ -56,8 +56,4 @@ def publish_proof?
   def post_params
     params.require(:account_identity_proof).permit(:post_status, :status_text)
   end
-
-  def set_body_classes
-    @body_classes = ''
-  end
 end