Bump xunit from 2.9.0 to 2.9.1 (#310)

Author: dependabot[bot]

src/MSBuildLocator.Tests/Microsoft.Build.Locator.Tests.csproj

@@ -10,7 +10,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
     <PackageReference Include="Shouldly" Version="4.2.1" />
-    <PackageReference Include="xunit" Version="2.9.0" />
+    <PackageReference Include="xunit" Version="2.9.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
   </ItemGroup>