Test

etc: add known hash for `/etc/shells` #1198

Job	Run time
install-against-stable	2m 52s
install-flake-against-unstable	3m 42s
test-unstable	9m 32s
test-stable	9m 36s
install-against-unstable	3m 26s
install-flake-against-stable	2m 45s
	31m 53s

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