#12415: Fix some doctests in sagenb
Needed for the new doctester framework

See http://trac.sagemath.org/sage_trac/ticket/12415
Don't doctest the data dir
Revert "#12415: Fix some doctests in sagenb"

Jeroen says this is no longer necessary.

This reverts commit 23da3557b5440698802bd8db3f7e1611f6ebfd1c.