GraphQL: remove monkey patch for resolve procs

Based on a comment by @engwan in !42111 (comment 418203222)

After this is done we could remove the monkey-patch in https://gitlab.com/gitlab-org/gitlab/blob/10b59855e641d30c1e1c104b37abe0e138fc6cf4/app/graphql/types/base_field.rb#L21-47 from the upgrade because of: https://github.com/rmosolgo/graphql-ruby/issues/3113#issuecomment-696772229

Once we've removed all the resolve procs (#247930 (closed)) then we should be able to remove this monkey patch.