Fix typo in `systems_to_torch` (#229) #116

Job	Run time
Lint Rust code (stable, x86_64-unknown-linux-gnu)	8s
check examples / benchmarks	2m 21s
ubuntu-20.04 / rust stable / static C library	8m 10s
ubuntu-20.04 / rust stable / release valgrind	8m 36s
ubuntu-20.04 / rust 1.64 / cmake 3.16	13m 59s
macos-11 / rust stable	8m 13s
windows-2019 / rust stable	19m 34s
	1h 1m 1s

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