fix(deps): update knative.dev/hack/schema digest to 306ce74 #1128

Namespace: <a href="https://detailurl.setting.custom-console-url-namespace.is.not.configured" rel="nofollow">ocp-serverless-tenant
PipelineRun: <a href="https://konflux-ui.apps.kflux-prd-rh02.0fk9.p1.openshiftapps.com/ns/ocp-serverless-tenant/pipelinerun/kn-eventing-heartbeats-115-on-pull-request-7nxc2" rel="nofollow">kn-eventing-heartbeats-115-on-pull-request-7nxc2

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Status	Duration	Name
✅ Succeeded	2 minutes	init
✅ Succeeded	2 minutes	clone-repository
✅ Succeeded	6 minutes	prefetch-dependencies
✅ Succeeded	9 minutes	build-images
✅ Succeeded	19 minutes	build-image-index
✅ Succeeded	11 minutes	deprecated-base-image-check
✅ Succeeded	10 minutes	sast-unicode-check
✅ Succeeded	13 minutes	clamav-scan
✅ Succeeded	13 minutes	ecosystem-cert-preflight-checks
✅ Succeeded	16 minutes	sast-snyk-check
✅ Succeeded	18 minutes	apply-tags
✅ Succeeded	18 minutes	build-source-image
✅ Succeeded	18 minutes	clair-scan
✅ Succeeded	13 minutes	rpms-signature-scan
✅ Succeeded	13 minutes	sast-shell-check
✅ Succeeded	13 minutes	push-dockerfile
✅ Succeeded	17 seconds	show-sbom