fix refs

docs/modules/ROOT/pages/jme3/advanced/terrain_collision.adoc

@@ -284,4 +284,4 @@ You should spawn high up in the area and fall down to the map, giving you a few
 See also:
 
 *  xref:tutorials:beginner/hello_terrain.adoc[Hello Terrain],
-*  xref:tutorials:advanced/terrain.adoc[Terrain]
+*  xref:jme3/advanced/terrain.adoc[Terrain]