Ignore pyproj to_proj4 warning when converting an AreaDefinition to a string

[djhoese]

This should resolve a majority of the warnings generated during pyresample and satpy tests. There are still many cases of tests using area_def.proj_str == other_area.proj_str, but we'll get to those later.

• Closes #xxxx
• Tests added
• Tests passed
• Passes git diff origin/main **/*py | flake8 --diff
• Fully documented

[codecov]

Codecov Report

Merging #512 (b2eab5e) into main (1357e3a) will decrease coverage by 0.01%.
The diff coverage is 97.46%.

@@            Coverage Diff             @@
##             main     #512      +/-   ##
==========================================
- Coverage   94.32%   94.31%   -0.01%     
==========================================
  Files          79       79              
  Lines       12905    12936      +31     
==========================================
+ Hits        12172    12201      +29     
- Misses        733      735       +2     

Flag	Coverage Δ
unittests	94.31% <97.46%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
pyresample/future/geometry/area.py	100.00% <ø> (ø)
pyresample/utils/cf.py	90.17% <ø> (ø)
pyresample/gradient/__init__.py	95.16% <83.33%> (+0.01%)	⬆️
pyresample/geometry.py	87.50% <95.65%> (-0.06%)	⬇️
pyresample/area_config.py	90.44% <100.00%> (ø)
pyresample/geo_filter.py	100.00% <100.00%> (ø)
pyresample/test/test_geometry/test_area.py	99.19% <100.00%> (+0.01%)	⬆️
pyresample/test/test_gradient.py	98.98% <100.00%> (ø)
pyresample/test/test_resample_blocks.py	98.62% <100.00%> (ø)
...le/test/test_resamplers/test_resampler_registry.py	96.55% <100.00%> (+0.63%)	⬆️

[coveralls]

Coverage: 93.843% (-0.0007%) from 93.843% when pulling b2eab5e on djhoese:bugfix-ignore-proj-warn-areastr into 1357e3a on pytroll:main.

[mraspaud]

LGTM, looks good with the context managers!