New terrain sdf (#57)

* New terrain sdf

* fix

* Added texture to terrain_world.sdf

* removed unnecessary terrain

---------

Co-authored-by: Mohammad Durrani <46766905+mdurrani808@users.noreply.github.com>

Author: Rishav-N

src/description/models/terrain_world/meshes/terrain.dae

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:c8b636870f6b43d20ce0df0c45a621f3f27fe0bc963bc5da1a8444710e6ea9b7
-size 5123210
+oid sha256:40abb75c4a11277529971212144f1d9056674d23904f66e9a4205bbe5c286502
+size 10791063

src/description/models/terrain_world/meshes/terrain_texture.png

@@ -9,17 +9,6 @@
             <uri>model://terrain_world/meshes/terrain.dae</uri>
           </mesh>
         </geometry>
-        <!-- <material>
-          <script>
-            <uri>model://terrain/meshes/scripts</uri>
-            <name>RepeatedSand/Diffuse</name>
-          </script> 
-        </material> -->
-        <material>
-          <ambient>0.85 0.76 0.52 1</ambient>
-          <diffuse>0.85 0.76 0.52 1</diffuse>
-          <specular>0.0 0.0 0.0 1</specular>
-        </material>
 
       </visual>
       <collision name="terrain_world_collision">