remove location_mod.rst from developer tests to prevent it showing up in searches of the docs

[hkershaw-brown]

Description:

Removed the location_mod.rst from developer tests to prevent it showing in the docs. Currently it is the first result when you search for location_mod, and it is out-of-date.

The actual location_mod documentation is in:
https://github.com/NCAR/DART/blob/main/assimilation_code/location/location_mod.rst

removed README, this is the same doc as location_mod.rst.

Fixes issue

fixes #796 (comment)

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.
  • I have updated the documentation accordingly.

Tests

Please describe any tests you ran to verify your changes.
Built documentation locally.

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

• Dataset needed for testing available upon request
• Dataset download instructions included
• No dataset needed

[mjs2369]

Good doc fix, approved