chore(deps): update actions/checkout action to v4 #997

Job	Run time
Run Tests / Bundle Integration	33m 3s
Publish Charm / Generate the Charm Matrix	5s
Run Tests / Individual charm's integration tests (controller)	32m 3s
Run Tests / Individual charm's integration tests (ui)	29m 10s
Run Tests / Lint Code (controller)	22s
Run Tests / Lint Code (ui)	22s
Run Tests / Unit Test (controller)	36s
Run Tests / Unit Test (ui)	38s
Run Tests / Check libraries (jupyter-controller) / Check libraries	28s
Run Tests / Check libraries (jupyter-controller) / Lint	8s
Run Tests / Check libraries (jupyter-ui) / Lint	11s
Run Tests / Check libraries (jupyter-ui) / Check libraries	22s
Run Tests / Terraform (controller) / Apply / Apply Terraform	5m 48s
Run Tests / Terraform (controller) / Check / Check Terraform	5s
Run Tests / Terraform (controller) / Lint / Lint Terraform	8s
Run Tests / Terraform (ui) / Apply / Apply Terraform	4m 52s
Run Tests / Terraform (ui) / Check / Check Terraform	9s
Run Tests / Terraform (ui) / Lint / Lint Terraform	10s
Publish Charm / Publish Charm (./charms/jupyter-ui)	18m 16s
Publish Charm / Publish Charm (./charms/jupyter-controller)	18m 0s
	2h 24m 56s

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