re-allow using RelatedNode as input to cardinality=one rel #1076

Job	Run time
Detect which file has changed	5s
prepare-environment / prepare	3s
markdown-lint	4s
python-lint	8s
yaml-lint	0s
action-lint	0s
documentation	55s
validate-generated-documentation	48s
unit-tests (3.11)	1m 16s
unit-tests (3.9)	1m 14s
unit-tests (3.13)	4m 39s
validate-documentation-style	7s
unit-tests (3.10)	1m 26s
integration-tests-latest-infrahub	8m 0s
unit-tests (3.12)	1m 36s
	20m 21s

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