Fix deprecated "compositor" usage in modifier definitions

[djhoese]

Noticed some deprecation warnings in my Polar2Grid tests.

• Closes #xxxx
• Tests added
• Fully documented
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.06%. Comparing base (6a4f2af) to head (0ad7c32).
Report is 305 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2916      +/-   ##
==========================================
- Coverage   96.06%   96.06%   -0.01%     
==========================================
  Files         373      373              
  Lines       54406    54406              
==========================================
- Hits        52267    52265       -2     
- Misses       2139     2141       +2     

Flag	Coverage Δ
behaviourtests	3.99% <ø> (ø)
unittests	96.16% <ø> (-0.01%)	⬇️

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[coveralls]

Pull Request Test Coverage Report for Build 11117022647

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.003%) to 96.161%

---

Files with Coverage Reduction	New Missed Lines	%
satpy/composites/config_loader.py	2	94.12%

Totals
Change from base Build 11109706783:	-0.003%
Covered Lines:	52499
Relevant Lines:	54595

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💛 - Coveralls