message: Drop obsolete link8_sc
diff: </joint>
  <link name="${arm_id}_link8"/>
  - <link name="${arm_id}_link8_sc"/>
  -
  - <joint name="${arm_id}_link8_sc_joint" type="fixed">
  - <parent link="${arm_id}_link8" />
  - <child link="${arm_id}_link8_sc" />
  - </joint>
  <joint name="${arm_id}_joint8" type="fixed">
  <origin rpy="0 0 0" xyz="0 0 0.107"/>
  