Remove the stale issue workflow

[billsacks]

From the CIME call today, the consensus was that, while this served a useful purpose in the past, it now can be more of a pain than a help. Now that we have restarted our biweekly CIME calls and are staying on top of issues better, this is no longer helpful.

Checklist

• My code follows the style guidelines of this project (black formatting)
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that exercise my feature/fix and existing tests continue to pass
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding additions and changes to the documentation