Bump actions/checkout from 3 to 4 #1699

Job	Run time
CLI responsiveness with latest Python	3m 53s
Downstream builds with Python 3.8	49s
Downstream builds with Python 3.9	1m 0s
Downstream builds with Python 3.10	53s
Python 3.8 on Linux	4m 44s
Downstream builds with Python 3.11	44s
Python 3.9 on Linux	3m 59s
Python 3.10 on Linux	4m 5s
Python 3.11 on Linux	3m 57s
Python 3.8 on Windows	5m 37s
Python 3.9 on Windows	5m 38s
Python 3.10 on Windows	5m 37s
Python 3.11 on Windows	6m 38s
Python 3.8 on macOS	4m 8s
Python 3.9 on macOS	4m 22s
Python 3.10 on macOS	3m 55s
Python 3.11 on macOS	3m 56s
Report coverage	45s
check	2s
	1h 4m 42s

Provide feedback