Removed insight-maven dependency from archetype-builder POM.

`insight-maven` seems not to be used at all in the `archetype-builder` project. On the other hand it causes build problems, because `archetype-builder` is always built while `insight-maven` is built only when `all` profile is active. It means that executing `mvn install` without `all` on fresh Fabric8 installation leads to "artifact insight-maven not found" error.

Feel free to revert if I'm missing something :) .