Make `signed_id_verifier_secret` a class attribute
Make `signed_id_verifier_secret` a class attribute

Followup: https://github.com/rails/rails/pull/42442

Edouard-chin/rails,kddeisz/rails,rails/rails,Vasfed/rails,rails/rails,MSP-Greg/rails,Erol/rails,rails/rails,MSP-Greg/rails,joonyou/rails,Erol/rails,Stellenticket/rails,Vasfed/rails,Envek/rails,kmcphillips/rails,yawboakye/rails,kmcphillips/rails,BlakeWilliams/rails,kddeisz/rails,BlakeWilliams/rails,Stellenticket/rails,joonyou/rails,Envek/rails,Stellenticket/rails,kddeisz/rails,esparta/rails,kmcphillips/rails,yawboakye/rails,lcreid/rails,yahonda/rails,esparta/rails,Stellenticket/rails,MSP-Greg/rails,BlakeWilliams/rails,rails/rails,joonyou/rails,georgeclaghorn/rails,EmmaB/rails-1,lcreid/rails,georgeclaghorn/rails,yahonda/rails,MSP-Greg/rails,Edouard-chin/rails,georgeclaghorn/rails,Envek/rails,yawboakye/rails,Erol/rails,yahonda/rails,georgeclaghorn/rails,lcreid/rails,EmmaB/rails-1,Edouard-chin/rails,yawboakye/rails,esparta/rails,joonyou/rails,EmmaB/rails-1,yahonda/rails,lcreid/rails,Vasfed/rails,Erol/rails,Envek/rails,kddeisz/rails,esparta/rails,kmcphillips/rails,Vasfed/rails,Edouard-chin/rails,BlakeWilliams/rails