Update actions/checkout action to v4 #406

Job	Run time
CodeQL Analyze	4m 59s
Build Package	0s
Build docs	0s
Scan Licenses	0s
Lint	1m 5s
Security Lint	1m 6s
SonarCloud	41s
Test Python 3.6 - ubuntu	6s
Test Python 3.7 - ubuntu	42s
Check Types	1m 13s
Test Python 3.8 - ubuntu	35s
Test Python 3.9 - ubuntu	34s
Test Python 3.6 - windows	2m 7s
Test Python 3.7 - windows	1m 29s
Test Python 3.8 - windows	1m 17s
Test Python 3.9 - windows	1m 20s
Test Python 3.6 - macos	1m 38s
Test Python 3.7 - macos	42s
Test Python 3.8 - macos	1m 10s
Test Python 3.9 - macos	1m 11s
Test Build Python ${{ matrix.py }} - ${{ matrix.os }}	0s
Publish Package	0s
Publish Docs	0s
	21m 55s

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