Improve stability of tests in PolyhedralGeometry #16983

Job	Run time
doctest (1.10, ubuntu-latest)	8m 38s
doctest (1.11-nightly, ubuntu-latest)	8m 41s
test (1.6, short, ubuntu-latest)	8m 41s
doctest (nightly, ubuntu-latest)	8m 40s
test (1.6, long, ubuntu-latest)	8m 38s
doctest (1.10, ubuntu-latest, depwarn=error)	8m 40s
test (1.10, short, ubuntu-latest)	8m 38s
test (1.10, long, ubuntu-latest)	8m 41s
doctest (1.10, macOS, RPTU)	8m 44s
test (1.11-nightly, short, ubuntu-latest)	8m 38s
test (1.11-nightly, long, ubuntu-latest)	8m 39s
test (nightly, short, ubuntu-latest)	8m 38s
test (nightly, long, ubuntu-latest)	8m 37s
test (1.10, short, ubuntu-latest, depwarn=error)	8m 38s
test (1.10, long, ubuntu-latest, depwarn=error)	8m 38s
test (1.10, short, macOS, RPTU)	8m 44s
test (1.10, long, macOS, RPTU)	8m 45s
test (1.10, book, ubuntu-latest)	8m 38s
test (nightly, book, ubuntu-latest)	8m 40s
	2h 44m 36s

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