Fix ABI L2 to only convert reflectances to percentages

[djhoese]

This is an add-on to #2607 where I realized after merging that the if statement (copied from the L1b reader) would be applied to any non-count data with units of "1". For L1b this is really only reflectances I think, but for L2 this could be many many other products. This PR changes this to be specifically calibration == "reflectance" which I think is safe enough for now.

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

[codecov]

Codecov Report

Merging #2608 (bd43ad6) into main (d762d1c) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2608   +/-   ##
=======================================
  Coverage   94.94%   94.94%           
=======================================
  Files         354      354           
  Lines       51487    51487           
=======================================
  Hits        48886    48886           
  Misses       2601     2601           

Flag	Coverage Δ
behaviourtests	4.26% <0.00%> (ø)
unittests	95.56% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
satpy/readers/abi_l2_nc.py	96.22% <100.00%> (ø)

[mraspaud]

LGTM, thank for the quick fix.

[coveralls]

Pull Request Test Coverage Report for Build 6612755225

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 95.515%

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Totals
Change from base Build 6610863260:	0.0%
Covered Lines:	49009
Relevant Lines:	51310

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💛 - Coveralls