Bump actions/download-artifact from 3 to 4 #186

Job	Run time
🏗️ Docker image	1m 27s
🧪 Python integration tests (3.8, pyserini)	5m 56s
🔍 Python code format (3.8)	6m 2s
🧪 Python integration tests (3.8, pyterrier)	6m 4s
🔍 Python code format (3.9)	4m 36s
🧪 Python integration tests (3.9, pyserini)	6m 4s
🧪 Python integration tests (3.9, pyterrier)	5m 4s
🔍 Python Lint (3.8)	5m 40s
🔍 Python Lint backend (3.8, pyserini)	4m 51s
🔍 Python Lint (3.9)	4m 22s
🔍 Python Lint backend (3.8, pyterrier)	5m 17s
🧪 Python unit tests (3.8)	5m 21s
🔍 Python Lint backend (3.9, pyserini)	5m 33s
🧪 Python unit tests (3.9)	5m 17s
🏗️ Python wheel (3.8)	23s
🔍 Python Lint backend (3.9, pyterrier)	6m 11s
🏗️ Python wheel (3.9)	26s
🚀 Create GitHub release	0s
🚀 Publish Python wheels	0s
🚀 Publish Docker image	0s
	1h 18m 34s

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