[refactoring] Remove redundant Project#getParentProject()

This method was just a synonym for EntityBase#getParentEntityId(),
and the name was misleading since it returned a UUID instead of
a project.

Change-Id: I6509e8ebbcaf6b7ad19e288f87a02215422871ac
Signed-off-by: Michael Ochmann <michael.ochmann@sap.com>
9 files changed