Documentation CI is failing

[sbryngelson]

See: https://github.com/MFlowCode/MFC/actions/runs/9085829960

Patching output file 341/345
Patching output file 342/345
Patching output file 343/345
Patching output file 344/345
Patching output file 345/345
type lookup cache used 560/65536 hits=823 misses=589
symbol lookup cache used 504/65536 hits=3114 misses=504
finished...
ninja: build stopped: subcommand failed.
Error: Process completed with exit code 1.
##[debug]Finishing: Build Documentation

[henryleberre]

This is actually related to #413

FAILED: fypp/post_process/m_variables_conversion.fpp.f90 /home/runner/work/MFC/MFC/build/fypp/post_process/m_variables_conversion.fpp.f90 
cd /home/runner/work/MFC/MFC/build && /home/runner/.local/bin/fypp -m re -I /home/runner/work/MFC/MFC/build/include/post_process -I /home/runner/work/MFC/MFC/src/post_process/include -I /home/runner/work/MFC/MFC/src/common/include -I /home/runner/work/MFC/MFC/src/common -D MFC_GNU -D MFC_POST_PROCESS -D MFC_COMPILER=\"GNU\" -D MFC_CASE_OPTIMIZATION=False --line-numbering --no-folding /home/runner/work/MFC/MFC/src/common/m_variables_conversion.fpp /home/runner/work/MFC/MFC/build/fypp/post_process/m_variables_conversion.fpp.f90
/home/runner/work/MFC/MFC/src/common/m_variables_conversion.fpp:7: error: include file 'case.fpp' not found [FyppFatalError]