Fix html build errors and warnings

[ppharris]

I've been seeing these html build errors for a while now and looking into it revealed a bunch of syntax errors associated with the RED namelist plus a duplicate entry for the l_red switch.

sphinx-build -b html -d build/doctrees   source build/html
Running Sphinx v7.3.7
making output directory... done
building [mo]: targets for 0 po files that are out of date
writing output... 
building [html]: targets for 104 source files that are out of date
updating environment: [new config] 104 added, 0 changed, 0 removed
reading sources... [100%] release_notes/contents
jules-lsm.github.io/user_guide/doc/source/namelists/contents.rst:17: WARNING: toctree contains reference to nonexisting document 'namelists/red_params.nml'
jules-lsm.github.io/user_guide/doc/source/namelists/red_parms.nml.rst:3: WARNING: Inline interpreted text or phrase reference start-string without end-string.
jules-lsm.github.io/user_guide/doc/source/namelists/red_parms.nml.rst:15: ERROR: Content block expected for the "nml:group" directive; none found.
looking for now-outdated files... none found
pickling environment... done
checking consistency... jules-lsm.github.io/user_guide/doc/source/namelists/red_parms.nml.rst: WARNING: document isn't included in any toctree
done
preparing documents... done
copying assets... copying static files... done
copying extra files... done
done
writing output... [100%] release_notes/contents
jules-lsm.github.io/user_guide/doc/source/namelists/jules_vegetation.nml.rst:658: WARNING: undefined label: 'argles, arthur pk, et al. (2020)'
jules-lsm.github.io/user_guide/doc/source/namelists/red_parms.nml.rst:3: WARNING: nml:lst reference target not found: JULES_RED
jules-lsm.github.io/user_guide/doc/source/release_notes/JULES7-1.rst:21: WARNING: nml:mem reference target not found: IMOGEN_RUN_LIST::l_drive_with_global_temps
generating indices... genindex nml-modindex done
writing additional pages... search done
copying images... [100%] input/interp_examples.png
dumping search index in English (code: en)... done
dumping object inventory... done
build succeeded, 7 warnings.

The HTML pages are in build/html.

Build finished. The HTML pages are in build/html.

[yaswant]

@ppharris We have plans to merge the jules docs back into the jules repository following the Git Migration. Can we migrate changes form this PR around that time?

[ppharris]

@yaswant Sure, nothing in this PR is time critical. I mainly wanted to put down a marker to get it fixed at some point.