ProjenYarnUpgrade is no longer required

[eladb]

Projen recently added a feature similar to ProjenYarnUpgrade, so I believe this feature can be deprecated from this module. Additionally, the way this workflow is currently implemented can potentially allow 3rd party libraries to get write permissions to repositories that are not configured using "restrictive mode" (the default GitHub token has write permissions).

I would highly recommend deprecating this workflow from here.

[pahud]

Thank you @eladb. Will deprecate this shortly.