chore(deps): update dependency verify.tunit to 31.15.0

Author: renovate[bot]

src/Directory.Packages.props

@@ -7,7 +7,7 @@
   <ItemGroup>
     <!-- Testing Framework -->
     <PackageVersion Include="TUnit" Version="1.12.125" />
-    <PackageVersion Include="Verify.TUnit" Version="31.13.0" />
+    <PackageVersion Include="Verify.TUnit" Version="31.15.0" />
     <PackageVersion Include="Verify.SourceGenerators" Version="2.5.0" />
     <PackageVersion Include="Microsoft.Testing.Extensions.CodeCoverage" Version="18.4.1" />