Update wiki/simulation/cad-to-urdf.md based on Nevin's feedback

Co-authored-by: Nevin Valsaraj <5763537+nevalsar@users.noreply.github.com>

Author: kodikarthik21

wiki/simulation/cad-to-urdf.md

@@ -48,7 +48,7 @@ base_link
 
 Inside the URDF file, a single joint looks like this:
 
-```
+```xml
 <joint name="shoulder_joint" type="revolute">
   <parent link="base_link"/>
   <child link="upper_arm_link"/>