I was not aware that Skype allowed multiple versions of itself to be installed. I’m not sure that this is intended behavior for Skype. In any case, I am not a Skype expert, so I’m not sure what the best solution would be for your situation, and I don’t know what the result would be if you follow the instructions at the link you posted above. I don’t know if that would remove one or both versions, so I would first try that and see what it gives you. If I were in your shoes I would probably just attempt to remove both versions and then install the desired version after that, leaving you with just one version.