Fix the `variable` link in `active_storage_overview.md` [ci skip]
Fix the `variable` link in `active_storage_overview.md` [ci skip]

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