chore(deps): update actions/checkout action to v4 #642

Job	Run time
Run Tests / Unit Test	25s
Publish Charm / Generate the Charm Matrix	2s
Run Tests / Lint Check	19s
Run Tests / Get integration environments	2s
Run Tests / Check libraries / Check libraries	33s
Run Tests / Check libraries / Lint	9s
Publish Charm / Publish Charm (./)	3m 28s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k mlflowserver-v1)	17m 8s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k mlflowserver-v2)	16m 6s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k xgboost-v1)	14m 40s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k huggingface)	19m 39s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k sklearn-v2)	14m 27s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k tensorflow)	14m 41s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k xgboost-v2)	20m 14s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k tf-serving)	16m 50s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k sklearn-v1)	16m 43s
Run Tests / Integration Test (build and deploy) (charm-integration --)	27m 37s
	3h 3m 3s

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