Steps (I had to do this last week; sharing the learning rather than just replicating the issue):
- Go to https://integration.wikimedia.org/ci/view/BrowserTests/
- Be logged in as someone with admin permissions (I think that's automatic for ldap/wmf)
- Go to the browser test you want to modify (e.g. the MobileFrontend Chrome enwiki BetaLabs one)
- Click "configure" in the upper-left of the project page.
- Scroll down to "Project Recipient List"
- Add/remove as needed.
- Press "Save" at the bottom of the page.