Update copyright note in documentation

[gerritholl]

Update the copyright notice in the readthedocs documentation.

• Closes Copyright notice out of date #231
• Passes git diff origin/main **/*py | flake8 --diff

[codecov]

Codecov Report

Merging #403 (8670bda) into main (0b35d70) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #403   +/-   ##
=======================================
  Coverage   93.83%   93.84%           
=======================================
  Files          65       65           
  Lines       11118    11124    +6     
=======================================
+ Hits        10433    10439    +6     
  Misses        685      685           

Flag	Coverage Δ
unittests	93.84% <ø> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
pyresample/test/test_swath.py	100.00% <0.00%> (ø)
pyresample/test/test_dask_ewa.py	98.92% <0.00%> (+0.06%)	⬆️

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[coveralls]

Coverage increased (+0.02%) to 93.665% when pulling 8670bda on gerritholl:doc-copyright into 0b35d70 on pytroll:main.