Updated unit test project packages

- Specifically coverlet.msbuild since that somehow stopped working at
  some point

Author: lord-executor

src/MaybeSharp.UnitTests/MaybeSharp.UnitTests.csproj

@@ -5,14 +5,14 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="coverlet.msbuild" Version="2.4.0">
+    <PackageReference Include="coverlet.msbuild" Version="3.1.0">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="FluentAssertions" Version="5.5.3" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.9.0" />
-    <PackageReference Include="NUnit" Version="3.11.0" />
-    <PackageReference Include="NUnit3TestAdapter" Version="3.11.2" />
+    <PackageReference Include="FluentAssertions" Version="6.1.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" />
+    <PackageReference Include="NUnit" Version="3.13.2" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.0.0" />
   </ItemGroup>
 
   <ItemGroup>