When deleting a version, if any issues have a fix-for version of the one being deleted, a screen offers to change the fix-for version, but that dropdown includes archived releases.

Delete Version: xxx

Confirm that you want to delete this version, and specify what is to be done with the issues currently matching this version.
Issues with this as a fix version: 1
(View the issues with this as a fix for version.)
Swap current fix version to:
Remove fix version from all issues.