Log Message:
shells/osh: remove, superseded by shells/etsh.

The project was renamed from osh to etsh in 2016.
The author himself was added as MAINTAINER for shells/osh as per request
in 2008.
However, it's reasonable to assume that they lost interest in the
package in the meantime.
In any case, we have shells/etsh now, making this an obsolete duplicate.