Removed old-style-cast from Plumed.h #2958

Job	Run time
codecheck / codecheck	43m 33s
conda / conda (ubuntu-20.04)	10m 12s
conda / conda (macos-12)	16m 42s
conda / conda (macos-14)	8m 30s
docker / docker (fedora39)	54m 22s
docker / docker (rocky8)	23m 41s
linux / linux (-doc-mpi-)	38m 50s
mac / macsimple (macos-12)	10m 22s
linux / linux (-mpi-)	48m 53s
mac / macports (macos-12)	15m 51s
mac / macports (macos-14)	9m 11s
linux / linux (-coverage-mpi-)	1h 2m 17s
mac / macsimple (macos-14)	4m 28s
mac / macports (+allmodules, macos-12)	25m 23s
linux / linux (-debug-)	30m 24s
linux / linux (-debug-mpi-)	40m 30s
linux / linux (-intel-)	43m 42s
linux / linux (-pycv-mpi-)	16m 40s
	8h 23m 31s

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