bird2: use official example config file

bird2: use official example config file

Using the openwrt example config (which seems to be a clone of the
official example2 config) leads to the following error:

    bird: /etc/bird.conf:138:15 syntax error, unexpected '/'

In addition, the previous configuration seems to me to be too
case-specific and cannot really be used as a template for a fresh
configuration.

Signed-off-by: Martin Schiller <[email protected]>
(cherry picked from commit 0490c7f39a1e53e2f49654aea16b015c8cc92380)