docs/contributing: Fix typo
docs/contributing: Fix typo

Signed-off-by: Alexander Dahl <e4ea294c062c525643df036a35ca579b905fa400@thorsis.com>

rauc/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc,ejoerns/rauc,ejoerns/rauc,rauc/rauc,jluebbe/rauc,jluebbe/rauc