Bump actions/setup-dotnet from 5 to 6 #5892

Job	Run time
Parallel Unit Tests (windows-latest)	4m 44s
Non-Parallel Unit Tests (macos-latest)	1m 20s
Parallel Unit Tests (macos-latest)	3m 29s
Parallel Unit Tests (ubuntu-latest)	3m 48s
Non-Parallel Unit Tests (ubuntu-latest)	2m 9s
Non-Parallel Unit Tests (windows-latest)	2m 59s
	18m 29s

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