chore(deps): update actions/checkout action to v4 #527

Job	Run time
Publish Charm / Generate the Charm Matrix	4s
Run Tests / Lint Code (operator)	21s
Run Tests / Lint Code (serving)	21s
Run Tests / Lint Code (eventing)	24s
Run Tests / Unit Test (operator)	27s
Run Tests / Unit Test (serving)	24s
Run Tests / Unit Test (eventing)	28s
Run Tests / Observability Integration Test	16m 32s
Run Tests / Integration Test	20m 30s
Run Tests / Check libraries / Check libraries	4s
Run Tests / Check libraries / Lint	10s
Run Tests / Terraform (eventing) / Apply	0s
Run Tests / Terraform (operator) / Apply	0s
Run Tests / Terraform (serving) / Apply	0s
Run Tests / Terraform (eventing) / Check / Check Terraform	7s
Run Tests / Terraform (eventing) / Lint / Lint Terraform	7s
Run Tests / Terraform (operator) / Check / Check Terraform	7s
Run Tests / Terraform (operator) / Lint / Lint Terraform	7s
Run Tests / Terraform (serving) / Check / Check Terraform	4s
Run Tests / Terraform (serving) / Lint / Lint Terraform	7s
Publish Charm / Publish Charm (./charms/knative-operator)	6m 43s
Publish Charm / Publish Charm (./charms/knative-serving)	2m 59s
Publish Charm / Publish Charm (./charms/knative-eventing)	3m 5s
	53m 11s

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