Correct unit to units in AuxCoord docstring

[jfrost-mo]

🚀 Pull Request

Description

Fixes #6347 by correcting the AuxCoord docstring.

---

Consult Iris pull request check list

---

Add any of the below labels to trigger actions on this PR:

• benchmark_this Request that this pull request be benchmarked to check if it introduces performance shifts

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.78%. Comparing base (a93085d) to head (73b47eb).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6348   +/-   ##
=======================================
  Coverage   89.78%   89.78%           
=======================================
  Files          90       90           
  Lines       23548    23548           
  Branches     4391     4391           
=======================================
  Hits        21143    21143           
  Misses       1662     1662           
  Partials      743      743           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[ESadek-MO]

Thanks @jfrost-mo, looks good to me, thanks for catching that!