In earlier macOS releases it happend a few times that a beta version of xcode commandline tools was made available to everyone by mistake, if you installed it you’d end up being offered beta releases in the future, or at least some times. To remove and avoid getting beta versions simply follow the below couple of steps.
Prevent macOS from offering you beta versions in the future
$ sudo rm -rf /Library/Developer/CommandLineTools/.beta
If you already have a beta version installed, remove it and reinstall a release version
$ sudo rm -rf /Library/Developer/CommandLineTools
$ xcode-select —install
Check for updates to refresh available packages
$ softwareupdate —list