Don't do JET.jl testing on pre-release

[KnutAM]

Ref #1295

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.25%. Comparing base (236eb50) to head (9de1e3d).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1296   +/-   ##
=======================================
  Coverage   94.25%   94.25%           
=======================================
  Files          40       40           
  Lines        6750     6750           
=======================================
  Hits         6362     6362           
  Misses        388      388           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.