Fix wrong case for PETSc

Convert doc/community/rst files to md

part of process of replacing all rst files with (MyST) md

Convert some of the rst files to md with ./rst2myst convert --config config.yaml *.rst

Need to manually fix

(petsc-developers-communication-channels)= to (petsc_developers_communication_channels)

Convert some of the rst files to md with ./rst2myst convert --config config.yaml *.rst

Need to manually fix

(petsc-developers-communication-channels)= to (petsc_developers_communication_channels)=

[include/petscerror.h](/include/petscerror.h.html) to <a href="PETSC_DOC_OUT_ROOT_PLACEHOLDER/include/petscerror.h.html">include/petscerror.h</a>

and friends

show more ...