Cannot enable text.module and ooyala.module at the same time

If you attempt to install text and ooyala modules at the same time you get a "Function already defined" error for _text_allowed_values(). This may happen if ooyala.module is pulled in first, then text.module is pulled in afterwards. Rather than rename the function, I think it'd be a good idea to simply remove the function entirely, since we don't actually allow a list values in the content field instance anyway. This patch just removes the function, since it doesn't really accomplish anything currently and is just left over cruft from when we were based on text.module.