Fix sign for virials #17

Job	Run time
codecheck / codecheck	1m 54s
docker / docker (fedora39)	8m 37s
conda / conda (ubuntu-20.04)	10m 53s
docker / docker (rocky8)	9m 40s
linux / linux (-doc-mpi-)	11m 20s
conda / conda (macos-12)	17m 31s
mac / macports (macos-12)	19m 55s
linux / linux (-mpi-)	11m 40s
conda / conda (macos-14)	6m 53s
mac / macports (macos-14)	10m 24s
linux / linux (-coverage-mpi-)	11m 13s
mac / macsimple (macos-12)	19m 51s
linux / linux (-debug-)	13m 13s
mac / macports (+allmodules, macos-12)	10m 37s
mac / macsimple (macos-14)	4m 22s
linux / linux (-debug-mpi-)	16m 12s
linux / linux (-intel-)	14m 19s
linux / linux (-pycv-mpi-)	10m 19s
	3h 28m 53s

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