Bump Verify.Xunit from 20.5.1 to 20.6.0 #1343

Job	Run time
build / build (windows-2022, /c/ProgramData/OpenTelemetry .NET AutoInstrumentation/logs)	17m 22s
build / build (ubuntu-20.04, /var/log/opentelemetry/dotnet)	5m 37s
build / build (macos-11, /var/log/opentelemetry/dotnet)	8m 16s
build-container / build-container (alpine, linux-musl)	5m 57s
build-container / build-container (centos, linux-glibc)	6m 44s
test-build-container (alpine, alpine, linux-musl)	12m 40s
test-build-container (centos, centos, linux-glibc)	11m 16s
test-build-container (debian, centos, linux-glibc)	11m 39s
test-build-native (windows-2022)	7m 45s
test-build-managed (net7.0, windows-2022)	14m 47s
test-build-managed (net7.0, ubuntu-20.04)	8m 35s
test-build-managed (net7.0, macos-11)	11m 11s
test-build-managed (net6.0, windows-2022)	20m 55s
test-build-managed (net6.0, ubuntu-20.04)	9m 6s
test-build-managed (net6.0, macos-11)	12m 26s
test-build-managed (net462, windows-2022)	15m 53s
test-build-windows-container-tests (windows-2022, windows-only)	20m 24s
build-nuget-packages / build-nuget-packages	9m 40s
test-nuget-packages	0s
	3h 30m 13s

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