chore(deps): update actions/checkout action to v4 #661

Job	Run time
Run Tests / Lint Check	31s
Run Tests / Get integration environments	5s
Publish Charm / Generate the Charm Matrix	3s
Run Tests / Unit Test	23s
Run Tests / Check libraries / Check libraries	40s
Run Tests / Check libraries / Lint	13s
Publish Charm / Publish Charm (./)	17m 34s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k mlflowserver-v1)	29m 45s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k tensorflow)	30m 21s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k sklearn-v2)	30m 36s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k tf-serving)	34m 57s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k sklearn-v1)	28m 33s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k xgboost-v2)	29m 47s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k huggingface)	31m 0s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k xgboost-v1)	28m 40s
Run Tests / Integration Test (build and deploy) (seldon-servers-integration -- -k mlflowserver-v2)	30m 7s
Run Tests / Integration Test (build and deploy) (charm-integration --)	34m 38s
	5h 27m 53s

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