Update metadata version of `opengever.base` 

There is an upgrade-step on a fresh installed installation.

https://github.com/4teamwork/opengever.core/blob/master/opengever/base/upgrades/configure.zcml#L146

https://github.com/4teamwork/opengever.core/blob/master/opengever/base/profiles/default/metadata.xml#L3