[icub]: fix some inertia properties in URDF

Author: costashatz

robots/icub/icub.urdf

@@ -1115,7 +1115,7 @@
    <inertial>
      <origin xyz="0 0 0"/>
      <mass value="0.000001"/>
-     <inertia ixx="1" ixy="0" ixz="0" iyy="1" iyz="0" izz="1"/>
+     <inertia ixx="0.000001" ixy="0.000001" ixz="0.000001" iyy="0.000001" iyz="0.000001" izz="0.000001"/>
    </inertial>
   </link>
   <joint name="fl_left_foot_contact" type="fixed">
@@ -1131,7 +1131,7 @@
    <inertial>
      <origin xyz="0 0 0"/>
      <mass value="0.000001"/>
-     <inertia ixx="1" ixy="0" ixz="0" iyy="1" iyz="0" izz="1"/>
+     <inertia ixx="0.000001" ixy="0.000001" ixz="0.000001" iyy="0.000001" iyz="0.000001" izz="0.000001"/>
    </inertial>
   </link>
   <joint name="fr_left_foot_contact" type="fixed">