Update IronPythonTest.csproj (#1603)

* Update IronPythonTest.csproj

Fix "System.ArgumentException: Unknown framework version 7.0" in step Test (net462)
Reference: nunit/nunit3-vs-adapter#987

* Update IronPythonTest.csproj

NUnit3TestAdapter 4.3.1 dropped netcoreapp2.1

Author: scott-xu

Src/IronPythonTest/IronPythonTest.csproj

@@ -19,7 +19,7 @@
   <ItemGroup>
     <PackageReference Include="NUnitLite" Version="3.13.3" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
-    <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.3.0" />
   </ItemGroup>
 
   <ItemGroup>