Bump xunit.runner.visualstudio from 2.8.0 to 2.8.1 #434

Job	Run time
Build and Test (debug, net35, windows-latest)	6m 56s
Build and Test (debug, net40, windows-latest)	6m 57s
Build and Test (debug, All, windows-latest)	13m 21s
Event File	2s
Build and Test (debug, All, ubuntu-latest)	5m 30s
Build and Test (debug, All, macos-latest)	5m 36s
Build and Test (release, net35, windows-latest)	6m 17s
Validate generated files	4m 30s
Build and Test (release, net40, windows-latest)	6m 9s
Build and Test (release, All, windows-latest)	12m 13s
Build and Test (release, All, ubuntu-latest)	5m 35s
Build and Test (release, All, macos-latest)	4m 26s
	1h 17m 32s

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