Fix useless block parameter
Fix useless block parameter

- Add underscore to `item` of block parameter
- This commit also fixes `warning: shadowing outer local variable`

rmosolgo/graphql-ruby,xuorig/graphql-ruby,rmosolgo/graphql-ruby,xuorig/graphql-ruby,nevesenin/graphql-ruby,xuorig/graphql-ruby,nevesenin/graphql-ruby,rmosolgo/graphql-ruby,nevesenin/graphql-ruby,rmosolgo/graphql-ruby,nevesenin/graphql-ruby