Add pandoc to the environment dependencies #7252

Job	Run time
clang-format	23s
no-crlf	20s
shellcheck	22s
cppcheck	12m 6s
flake8	30s
pre-commit-hooks	1m 23s
vale	34s
pydocstyle	26s
mypy	39s
forbidden_types	19s
isort	18s
unused_names	18s
black	35s
copyright_headers	25s
lychee_IGNORED	25s
pylint	51s
rstcheck	31s
sphinx-rtd	3m 53s
sphinx-conda	0s
build_macos (macos-latest, clang, openmp, mpi, python, gsl, ltdl, boost, hdf5, optimize, warning)	16m 0s
build_linux (ubuntu-22.04, gcc, openmp, mpi, python, gsl, ltdl, boost, hdf5, sionlib, libneurosim...	30m 57s
build_linux (ubuntu-22.04, gcc, mpi, python, gsl, ltdl, boost, optimize, warning)	16m 55s
build_linux (ubuntu-22.04, gcc, openmp, python, gsl, ltdl, boost, optimize, warning)	17m 8s
build_linux (ubuntu-22.04, gcc, boost, optimize, warning)	11m 39s
build_linux (ubuntu-22.04, gcc, optimize, warning)	9m 53s
	2h 6m 50s

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