fix: fix conflict with #181

This commit fixes a unhandeled conflict that is created when both #181
and #157 are merged.

franka_gazebo/launch/panda.launch

@@ -11,8 +11,8 @@
   <!-- Robot Customization -->
   <arg name="arm_id"      default="panda" doc="Name of the panda robot to spawn" />
   <arg name="use_gripper" default="true"  doc="Should a franka hand be mounted on the flange?" />
-  <arg name="transmission" default="effort" doc="Transmission type used for arm joints. One of position, velocity, effort." />
   <arg name="controller"  default=" "     doc="Which example controller should be started? (One of {cartesian_impedance,model,force}_example_controller)" />
+  <arg name="transmission" default="effort" doc="Transmission type used for arm joints. One of position, velocity, effort." />
   <arg name="x"           default="0"     doc="How far forward to place the base of the robot in [m]?" />
   <arg name="y"           default="0"     doc="How far leftwards to place the base of the robot in [m]?" />
   <arg name="z"           default="0"     doc="How far upwards to place the base of the robot in [m]?" />