Update NuGet packages for .Test project

Author: christophwille

ICSharpCode.AvalonEdit.Tests/ICSharpCode.AvalonEdit.Tests.csproj

@@ -24,10 +24,10 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
-    <PackageReference Include="NUnit" Version="3.13.3" />
-    <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.2.0" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+    <PackageReference Include="NUnit" Version="3.14.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\ICSharpCode.AvalonEdit\ICSharpCode.AvalonEdit.csproj" />