Fully remove deprecated functionality

[teutoburg]

All of those had warnings raised for two minor versions, explicitly stating the version of full removal (v0.12 in this case).

[codecov]

Codecov Report

❌ Patch coverage is 73.33333% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.50%. Comparing base (070069a) to head (f48b6d8).

Files with missing lines	Patch %	Lines
scopesim/optics/image_plane.py	83.33%	2 Missing ⚠️
scopesim/effects/data_container.py	50.00%	1 Missing ⚠️
scopesim/server/database.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #963      +/-   ##
==========================================
- Coverage   75.60%   75.50%   -0.11%     
==========================================
  Files          70       69       -1     
  Lines        8983     8935      -48     
==========================================
- Hits         6792     6746      -46     
+ Misses       2191     2189       -2     

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