fix: revert back to SimpleBase 1.3.1

The 1.4.1 is causing VS 2017 not to find the tests.

Author: richardschneider

src/IpfsCore.csproj

@@ -49,7 +49,7 @@
     <PackageReference Include="Google.Protobuf" Version="3.8.0" />
     <PackageReference Include="Newtonsoft.Json" Version="12.0.2" />
     <PackageReference Include="Portable.BouncyCastle" Version="1.8.5" />
-    <PackageReference Include="SimpleBase" Version="1.4.1" />
+    <PackageReference Include="SimpleBase" Version="1.3.1" />
     <PackageReference Include="Grpc.Tools" Version="1.21.0" PrivateAssets="All" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-beta2-19270-01" PrivateAssets="All" />
     <PackageReference Include="Microsoft.VisualStudio.Threading.Analyzers" Version="16.0.102" PrivateAssets="All" />