Bump NUnit3TestAdapter from 3.13.0 to 3.15.1 in /Solutions (#1)

Bumps [NUnit3TestAdapter](https://github.com/nunit/nunit3-vs-adapter) from 3.13.0 to 3.15.1.
- [Release notes](https://github.com/nunit/nunit3-vs-adapter/releases)
- [Commits](nunit/nunit3-vs-adapter@V3.13...V3.15.1)

Signed-off-by: @idg10

Solutions/Ais.Net.Specs/Ais.Net.Specs.csproj

@@ -10,7 +10,7 @@
 
   <ItemGroup>
     <PackageReference Include="System.Memory" Version="4.5.3" />
-    <PackageReference Include="NUnit3TestAdapter" Version="3.13.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="3.15.1" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.2.0" />
     <PackageReference Include="SpecFlow.NUnit.Runners" Version="3.0.225" />
     <PackageReference Include="SpecFlow.Tools.MsBuild.Generation" Version="3.0.225" />