Update archetype version in plugin documentation to 2.9

When 2.9 is released plugin developers should be able to copy and
paste the archetype command from the plugin documentation. For this
the version should match the released version. The command will work
only after the 2.9 plugin artifacts have been published to Maven
Central.

Change-Id: I4188c3740536f31eb49be2091cc89630da6cda96
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
1 file changed