fix: remove _r8 from .nml files

[hkershaw-brown]

Description:

This pull request removes the _r8 from .nml files
This _r8 causes errors in namelist reads when reading values (e.g. 0.0_r8)

Fixes issue

fixes #1055

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.
See #1055 namelist read code example.
Searched for *.nml files with _r8 (and _r8, _digits13, i8, i4)

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