Bump NUnit from 3.12.0 to 3.13.1

Bumps [NUnit](https://github.com/nunit/nunit) from 3.12.0 to 3.13.1.
- [Release notes](https://github.com/nunit/nunit/releases)
- [Changelog](https://github.com/nunit/nunit/blob/master/CHANGES.md)
- [Commits](nunit/nunit@v3.12...v3.13.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

src/MW5/packages.config

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="NUnit" version="3.12.0" targetFramework="net46" />
+  <package id="NUnit" version="3.13.1" targetFramework="net46" />
   <package id="System.Data.SQLite.Core" version="1.0.113.7" targetFramework="net46" />
 </packages>

test/MW5.Api.Test/packages.config

@@ -2,7 +2,7 @@
 <packages>
   <package id="Castle.Core" version="4.4.1" targetFramework="net46" />
   <package id="Moq" version="4.16.0" targetFramework="net46" />
-  <package id="NUnit" version="3.12.0" targetFramework="net46" />
+  <package id="NUnit" version="3.13.1" targetFramework="net46" />
   <package id="System.Runtime.CompilerServices.Unsafe" version="5.0.0" targetFramework="net46" />
   <package id="System.Threading.Tasks.Extensions" version="4.5.4" targetFramework="net46" />
   <package id="System.ValueTuple" version="4.5.0" targetFramework="net46" />

test/MW5.Test/packages.config

@@ -3,7 +3,7 @@
   <package id="Castle.Core" version="4.4.1" targetFramework="net46" />
   <package id="Moq" version="4.16.0" targetFramework="net46" />
   <package id="Newtonsoft.Json" version="12.0.3" targetFramework="net46" />
-  <package id="NUnit" version="3.12.0" targetFramework="net46" />
+  <package id="NUnit" version="3.13.1" targetFramework="net46" />
   <package id="System.Runtime.CompilerServices.Unsafe" version="5.0.0" targetFramework="net46" />
   <package id="System.Threading.Tasks.Extensions" version="4.5.4" targetFramework="net46" />
   <package id="System.ValueTuple" version="4.5.0" targetFramework="net46" />

test/MW5.Tools.Test/packages.config

@@ -2,7 +2,7 @@
 <packages>
   <package id="Castle.Core" version="4.4.1" targetFramework="net46" />
   <package id="Moq" version="4.16.0" targetFramework="net46" />
-  <package id="NUnit" version="3.12.0" targetFramework="net46" />
+  <package id="NUnit" version="3.13.1" targetFramework="net46" />
   <package id="System.Runtime.CompilerServices.Unsafe" version="5.0.0" targetFramework="net46" />
   <package id="System.Threading.Tasks.Extensions" version="4.5.4" targetFramework="net46" />
   <package id="System.ValueTuple" version="4.5.0" targetFramework="net46" />