Update xUnit.net to version 2.8.0

Author: 0xced

tests/Serilog.Formatting.Log4Net.Tests.csproj

@@ -17,8 +17,8 @@
     <PackageReference Include="Serilog.Enrichers.Environment" Version="2.3.0" />
     <PackageReference Include="Serilog.Enrichers.Thread" Version="3.1.0" />
     <PackageReference Include="Verify.Xunit" Version="24.1.0" />
-    <PackageReference Include="xunit" Version="2.7.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.8" PrivateAssets="all" />
+    <PackageReference Include="xunit" Version="2.8.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.0" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>