Now that unit tests are run on GitHub Actions in all three major
engines and for multiple custom jQuery builds, the request for PR
authors to run unit tests locally and confirm they pass is needless
overhead; let's drop the checkbox.
Closes gh-5261
The EasyCLA status check is required so this won't get missed. The old JSF CLA
is dead, the provided link doesn't return meaningful information. There's no
good replacement link for the old CLA; PR authors are just supposed to sign the
new CLA by clicking on a link posted by the EasyCLA bot when they submit their
first PR since EasyCLA was enabled for the repo.
Closes gh-4937
