Bump NUnit from 4.3.0 to 4.3.1 in /src (#826)

Author: dependabot[bot]

src/Directory.Packages.props

@@ -15,7 +15,7 @@
     <PackageVersion Include="Microsoft.EntityFrameworkCore.Sqlite" Version="9.0.0" />
     <PackageVersion Include="Microsoft.EntityFrameworkCore.SqlServer" Version="9.0.0" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
-    <PackageVersion Include="NUnit" Version="4.3.0" />
+    <PackageVersion Include="NUnit" Version="4.3.1" />
     <PackageVersion Include="NUnit3TestAdapter" Version="4.6.0" />
     <PackageVersion Include="Polyfill" Version="7.5.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.147" />