review_criteria: remove specific call-out of Travis-CI
review_criteria: remove specific call-out of Travis-CI

There are many continuous integration providers, hosted and not.
Travis-CI changed their open source policy and many packages moved away.
GitHub Actions is the most convenient for projects on GitHub first
considering CI, but docs are accessible enough we don't need to plug
them specifically.

openjournals/joss,openjournals/joss,openjournals/joss