pingus: correct RDEPENDS

fixes for latest HEADs:
ERROR: QA Issue: /home/Superandy/data/oe-core/sources/meta-games/recipes-games/pingus/pingus_0.7.6.bb: Variable RDEPENDS is set as not being package specific, please fix this.                  | ETA:  --:--:--

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>