Bump IronPython from 3.4.1 to 3.4.2 in /docs/csharp/advanced-topics/interop/snippets/dynamic-iron-python-walkthrough in the dotnet group

Bump IronPython from 3.4.1 to 3.4.2 in /docs/csharp/advanced-topics/interop/snippets/dynamic-iron-python-walkthrough in the dotnet group #1839