Fixes for remaining documentation warnings in #546

[c-merchant]

Description:

This pr fixes the documentation warnings in:
index.rst -> added new_model template and fluxnetfull_to_obs to toctree
models/lorenz_96_tracer_advection/readme.rst -> removed unnecessary indentation in line 66
observations/obs_converters/Ameriflux/level4_to_obs.rst -> uncapitalized "f" for fluxnetfull_to_obs.rst

Fixes issue

This pr resolves the remaining documentation warnings in Issue #546.
fixes #546

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.
After these changes, I ran "make clean" then "make html" to verify that no warnings were left.

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

[hkershaw-brown]

approved!