chore(deps): update dependency snapshooter.nunit to 0.15.0

Author: renovate[bot]

tests/Directory.Build.props

@@ -16,6 +16,6 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageReference Include="coverlet.collector" Version="6.0.1" />
     <PackageReference Include="GitHubActionsTestLogger" Version="2.3.3" />
-    <PackageReference Include="Snapshooter.NUnit" Version="0.13.0" />
+    <PackageReference Include="Snapshooter.NUnit" Version="0.15.0" />
   </ItemGroup>
 </Project>