chore(deps): update actions/checkout action to v4 #647

Job	Run time
Run Tests / Lint Check	19s
Run Tests / Get integration environments	3s
Publish Charm / Generate the Charm Matrix	2s
Run Tests / Unit Test	24s
Run Tests / Check libraries / Check libraries	24s
Run Tests / Check libraries / Lint	10s
Publish Charm / Publish Charm (./)	3m 12s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k mlflowserver-v1)	6h 0m 15s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k mlflowserver-v2)	14m 18s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k xgboost-v1)	14m 36s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k huggingface)	17m 57s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k sklearn-v2)	14m 6s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k tensorflow)	12m 37s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k xgboost-v2)	15m 40s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k tf-serving)	14m 36s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k sklearn-v1)	14m 11s
Run Tests / Integration Test (build and deploy) (charm-integration --)	18m 26s
	8h 21m 16s

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