Updated radar observation docs

[braczka]

Description:

The obs converter radar documentation was deprecated and pointed to an old google archive version (OPAWS) that converted DORADE and FORAY radar formats. New documentation now points to pyOPAWS converter developed by NOAA and capable of converting more commonly used NEXRAD radar format. pyOPAWS is a viable option for both WRF and MPAS radar DA applications.

Fixes issue

Fixes issue #827 .

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Documentation changes needed?

• My change requires a change to the documentation.
• [ X] I have updated the documentation accordingly.

Tests

I have run the pyOPAWS test case within the example instructions using Derecho. I have provided Quickstart instructions
within the new documentation that provides required steps for both generating diagnostic plots and radar obs_seq.out files.

Checklist for merging

• Updated changelog entry
• Documentation updated
• Update conf.py

Checklist for release

• Merge into main
• Create release from the main branch with appropriate tag
• Delete feature-branch

Testing Datasets

Testing NEXRAD datasets already provided with the pyOPAWS package.