Cannot remove "Internal test track" build from Google Play Console
It is possible to discard the release by creating a new release without a bundle or APK, inserting a release name, which is required, and completing the process.
We found that while there is no remove, we had to add an empty version which replaced the test version. This was a huge problem for us as the test version was in violation of permissions rules and our production code was not, but the production app was pulled from the Play store... Yikes. Adding a remove or delete would be soooo much more intuitive.
I would upload your next alpha to the internal test track and promote it to the alpha/closed track. You will still have a build in the internal test track, but at least it is a relevant build.