Follow-up from "Add GraphQL to the Environment Rollback Components"

The following discussion from !75560 (merged) should be addressed:

• @jiaan started a discussion: (+2 comments)

  Question (non-blocking): Is there anyway we could avoid using a question mark as an API property? And if we absolutely have to, WDYT about replacing this and other instances with a constant like IS_LAST_KEY? I think that would make this a bit more readable. As it stands the string key and the question mark mixed in with with optional chaining made me do a double take. 👀