Currently the accept process document creates 0 connectors. Instead, it
creates empty custom shapes: this commit fixes the loop, so that only
one of them is created.

The whole purpose of the follow sibling axis is that N - 1 connectors
are created for N shapes, not N connectors.

Change-Id: I54244c7615b83f607ef53a4ff8d01d3c9594856e
Reviewed-on: https://gerrit.libreoffice.org/64122Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins