Update dependency NUnit to v4

Author: dependencyupdates[bot]

src/TestHelper/TestHelper.csproj

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="NUnit" Version="3.14.0" />
+    <PackageReference Include="NUnit" Version="4.6.1" />
     <PackageReference Include="NUnit.Analyzers" Version="4.6.0" />
   </ItemGroup>
 

src/TimeoutMigrationTool.Tests/TimeoutMigrationTool.Tests.csproj

@@ -11,7 +11,7 @@
   <ItemGroup>
     <PackageReference Include="GitHubActionsTestLogger" Version="3.0.4" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.6.0" />
-    <PackageReference Include="NUnit" Version="3.14.0" />
+    <PackageReference Include="NUnit" Version="4.6.1" />
     <PackageReference Include="NUnit.Analyzers" Version="4.6.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="6.2.0" />
   </ItemGroup>