doc: Remove the bdb translator documentation

The translator was removed in ea08bf886732d9680f2d6de19f3d68908a55143b.

Change-Id: I3d124be9e3962a54f0ab0247cfd4867b815f4a17
Signed-off-by: Lubomir Rintel <lubo.rintel@gooddata.com>
Reviewed-on: http://review.gluster.org/5483
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>