Remove unused constant `FileSystemResolver::EXTENSIONS`
Remove unused constant `FileSystemResolver::EXTENSIONS`

Following up #42004

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