Rename lamp off state from 'none' to 'off'

[oczoske]

The original name "none" was converted to None somewhere. The new term "off" should be safe.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 75.11%. Comparing base (0cc827a) to head (d89055d).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
scopesim/effects/metis_wcu/metis_wcu.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #835   +/-   ##
=======================================
  Coverage   75.11%   75.11%           
=======================================
  Files          69       69           
  Lines        8777     8777           
=======================================
  Hits         6593     6593           
  Misses       2184     2184           

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