readme: be more concise

[ptrebert]

I just noticed that the short description of the update_metadata script unnecessarily introduces a new name, which makes its intent less clear: what are "metafiles"? They are metadata files, and to make it obvious what is meant by that, it could also mention an example like so: ...metadata files such as the license or citation info.

A second point: the description speaks of workflows only, but all (!) CUBI repositories must be initialized with a license, citation info etc. (see the readme in the metadata files repo, it is quite clear about that).

[svenbioinf]

updated readme

[svenwillger]

Issue addressed by Sven B