hdl._nir: AssignmentList: fix comb_edges_to #3562

Job	Run time
check-links	51s
test (3.8)	2m 22s
document	46s
smoke (amaranth-lang/amaranth-boards)	30s
test (3.9)	2m 13s
smoke (amaranth-lang/amaranth-stdio)	35s
test (3.10)	2m 13s
smoke (amaranth-lang/amaranth-soc)	37s
test (3.11)	2m 46s
test (3.12)	3m 55s
test (pypy-3.8)	5m 18s
test (pypy-3.9)	4m 58s
test (pypy-3.10)	4m 44s
test (3.13-dev)	2m 57s
publish-docs	14s
publish-docs-dev	0s
required	1s
publish-package	46s
publish-schemas	13s
publish-release	0s
	35m 59s

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