fix(schema): fix OASv3 schema generation fails when model used in @On… #6444

Job	Run time
lint (18.x)	3m 32s
test-core (18.x)	2m 58s
test-integration (ubuntu-latest, 16.x)	3m 47s
test-integration (ubuntu-latest, 18.x)	4m 41s
test-integration (ubuntu-latest, 19.x)	3m 37s
test-integration (macos-latest, 18.x)	6m 17s
test-integration (windows-latest, 18.x)	12m 5s
test-orm (18.x)	2m 55s
test-platform (18.x)	3m 15s
test-specs (18.x)	4m 22s
test-graphql (18.x)	2m 57s
test-third-parties (18.x)	3m 36s
test-security (18.x)	2m 57s
test-formio (18.x)	2m 44s
deploy-packages	0s
publish-docs	0s
	59m 43s

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