relink: retire the command

relink: retire the command

Back in the olden days, when all objects were loose and rubber boots were
made out of wood, it made sense to try to share (immutable) objects
between repositories.

Ever since the arrival of pack files, it is but an anachronism.

Let's move the script to the contrib/examples/ directory and no longer
offer it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>