[graphics/ogre-next] Always PREFER robotpkg package

The ubuntu-24.04 ogre-next package has a couple of undefined symbols, that
makes it unusable with graphics/gz-rendering.

An issue has been reported, but it does not seem to have made any progress
since then:
https://bugs.launchpad.net/ubuntu/+source/ogre-next/+bug/2063359

Author: Anthony Mallet

graphics/ogre-next/depend.mk

@@ -2,28 +2,21 @@
 # Created:			Anthony Mallet on Wed, 12 Feb 2025
 #
 
-DEPEND_DEPTH:=			${DEPEND_DEPTH}+
-OGRE_NEXT_DEPEND_MK:=		${OGRE_NEXT_DEPEND_MK}+
+DEPEND_DEPTH:=		${DEPEND_DEPTH}+
+OGRE_NEXT_DEPEND_MK:=	${OGRE_NEXT_DEPEND_MK}+
 
 ifeq (+,$(DEPEND_DEPTH))
-DEPEND_PKG+=			ogre-next
+DEPEND_PKG+=		ogre-next
 endif
 
 ifeq (+,$(OGRE_NEXT_DEPEND_MK)) # ------------------------------------------
 
-include ../../mk/robotpkg.prefs.mk # for OPSYS
-ifeq (Ubuntu,${OPSYS})
-  ifneq (,$(filter 18.04% 20.04% 22.04%,${OS_VERSION}))
-    PREFER.ogre-next?=	robotpkg
-  endif
-  PREFER.ogre-next?=	system
-endif
 PREFER.ogre-next?=	robotpkg
 
 DEPEND_USE+=		ogre-next
 
-DEPEND_ABI.ogre-next?=		ogre-next>=2
-DEPEND_DIR.ogre-next?=		../../graphics/ogre-next
+DEPEND_ABI.ogre-next?=	ogre-next>=2
+DEPEND_DIR.ogre-next?=	../../graphics/ogre-next
 
 SYSTEM_SEARCH.ogre-next=\
   'include/OGRE-{Next,[0-9]*}/Ogre.h'	\
@@ -32,4 +25,4 @@ SYSTEM_SEARCH.ogre-next=\
 
 endif # OGRE_NEXT_DEPEND_MK ------------------------------------------------
 
-DEPEND_DEPTH:=			${DEPEND_DEPTH:+=}
+DEPEND_DEPTH:=		${DEPEND_DEPTH:+=}