fix template preview images; add obj (o3de#586)

* add obj format to importer registry
* update template preview images
* fix Ros2RoboticManipulationTemlate template.json
---------
Signed-off-by: Jan Hanca <[email protected]>

Author: jhanca-robotecai

Templates/Ros2FleetRobotTemplate/Template/Registry/sceneassetimporter.setreg

@@ -11,7 +11,8 @@
 					".fbx",
 					".stl",
 					".gltf",
-					".glb"
+					".glb",
+					".obj"
 				]
 			},
 			"MaterialConverter": 

Templates/Ros2FleetRobotTemplate/Template/preview.png

@@ -11,7 +11,8 @@
 					".fbx",
 					".stl",
 					".gltf",
-					".glb"
+					".glb",
+					".obj"
 				]
 			},
 			"MaterialConverter":