Remove icinga-prepare-dirs from icinga-bin package

`icinga-prepare-dirs` was part of the package common and bin. Since it
was added with 2.2.0 to common with a man page I would expect this to be
the right place so I removed it from bin.

fixes #7740

Signed-off-by: Gunnar Beutner <gunnar.beutner@netways.de>