Restrict JsonNet compat tests to v1.x of JSON lib

To avoid testing with v4.x when that is released later.

Author: angularsen

UnitsNet.Serialization.JsonNet.CompatibilityTests/UnitsNet.Serialization.JsonNet.CompatibilityTests.csproj

@@ -17,7 +17,7 @@
 
   <ItemGroup>
     <!--Get the latest released version of UnitsNet.Serialization.JsonNet in Nuget-->
-    <PackageReference Include="UnitsNet.Serialization.JsonNet" Version="*" />
+    <PackageReference Include="UnitsNet.Serialization.JsonNet" Version="1.3.*" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.3.0" />
     <PackageReference Include="xunit" Version="2.3.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />