lib.wiring: fix Signature.is_compliant docstring [0.5 backport] #3564

Job	Run time
test (3.8)	2m 42s
test (3.9)	2m 24s
smoke (amaranth-lang/amaranth-boards)	37s
test (3.10)	2m 13s
check-links	44s
smoke (amaranth-lang/amaranth-stdio)	43s
test (3.11)	2m 37s
smoke (amaranth-lang/amaranth-soc)	37s
test (3.12)	3m 27s
document	49s
test (pypy-3.8)	5m 17s
test (pypy-3.9)	4m 59s
test (pypy-3.10)	5m 18s
test (3.13-dev)	3m 3s
publish-docs	9s
publish-docs-dev	0s
required	1s
publish-schemas	7s
publish-package	38s
publish-release	0s
	36m 25s

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