Move fci_l1c_fdhsi and viirs_l2_cloud_mask_nc to full deprecation

[ameraner]

This PR moves two readers that were pending deprecation since 4 years (FCI #1713) and 2 years (VIIRS, 65511ec, #2531) to full deprecation.

Now, instead of a warning, a ValueError will be raised, still pointing to the new reader name.

• Closes Move fci_l1c_fdhsi reader from pending to full deprecation #1713

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.29%. Comparing base (4f0befb) to head (8b5be7a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3298      +/-   ##
==========================================
- Coverage   96.30%   96.29%   -0.02%     
==========================================
  Files         463      463              
  Lines       58863    58863              
==========================================
- Hits        56689    56683       -6     
- Misses       2174     2180       +6     

Flag	Coverage Δ
behaviourtests	3.61% <100.00%> (ø)
unittests	96.38% <100.00%> (-0.02%)	⬇️

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[coveralls]

Pull Request Test Coverage Report for Build 19360172961

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall first build on update_deprecated_readers at 96.372%

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Totals
Change from base Build 19293346095:	96.4%
Covered Lines:	56561
Relevant Lines:	58690

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💛 - Coveralls