DM-52345: Add note about status of this library

[dhirving]

Add a note to the README stating that this package is no longer used by the stack or maintained.

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.24%. Comparing base (79127c2) to head (76c3a96).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #23   +/-   ##
=======================================
  Coverage   93.24%   93.24%           
=======================================
  Files          50       50           
  Lines        3509     3509           
  Branches      336      336           
=======================================
  Hits         3272     3272           
  Misses        159      159           
  Partials       78       78           

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[timj]

I am wondering if we want to trigger one final PyPI release (it won't happen manually so we'll have to force it when this merges)