Fixes to documentation generators for PlumedToHTML (#1081) #2894

Job	Run time
linux / linux (-doc-mpi-)	38m 31s
linux / linux (-mpi-)	48m 52s
linux / linux (-coverage-mpi-)	59m 50s
linux / linux (-debug-)	30m 11s
linux / linux (-debug-mpi-)	40m 6s
linux / linux (-intel-)	45m 16s
linux / linux (-pycv-mpi-)	17m 50s
codecheck / codecheck	39m 49s
conda / conda (ubuntu-20.04)	10m 24s
conda / conda (macos-12)	19m 16s
conda / conda (macos-14)	8m 26s
mac / macports (macos-12)	17m 39s
mac / macports (macos-14)	22m 54s
mac / macports (+allmodules, macos-12)	24m 14s
docker / docker (fedora39)	21m 17s
docker / docker (rocky8)	24m 1s
mac / macsimple (macos-12)	9m 8s
mac / macsimple (macos-14)	4m 28s
	8h 2m 12s

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