lib.wiring: fix Signature.is_compliant docstring #3539

Job	Run time
check-links	43s
document	52s
smoke (amaranth-lang/amaranth-boards)	36s
test (3.8)	2m 25s
smoke (amaranth-lang/amaranth-stdio)	43s
test (3.9)	2m 16s
smoke (amaranth-lang/amaranth-soc)	40s
test (3.10)	2m 6s
test (3.11)	2m 36s
test (3.12)	3m 22s
test (pypy-3.8)	5m 0s
test (pypy-3.9)	4m 48s
test (pypy-3.10)	4m 41s
test (3.13-dev)	2m 59s
publish-docs	5s
publish-docs-dev	0s
required	1s
publish-package	39s
publish-schemas	8s
publish-release	0s
	34m 40s

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