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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.06%. Comparing base (6a4f2af) to head (0ad7c32). Report is 18 commits behind head on main.

Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/pytroll/satpy/pull/2916/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | Coverage Δ | | |---|---|---| | [behaviourtests](https://app.codecov.io/gh/pytroll/satpy/pull/2916/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | `3.99% <ø> (ø)` | | | [unittests](https://app.codecov.io/gh/pytroll/satpy/pull/2916/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | `96.16% <ø> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[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%
<!--	Total:	2		-->

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

---

💛 - Coveralls