Apply rubocop Rails/FindBy rule everywhere

We didn't detect these cases because by default the rule only searches
for offenses in `app/models/`.

app/controllers/verification/sms_controller.rb

@@ -58,7 +58,7 @@ class Verification::SmsController < ApplicationController
     def verified_user
       return false unless params[:verified_user]
 
-      @verified_user = VerifiedUser.by_user(current_user).where(id: params[:verified_user][:id]).first
+      @verified_user = VerifiedUser.by_user(current_user).find_by(id: params[:verified_user][:id])
     end
 
     def redirect_to_next_path