Explicitly disable tendon range limits and actuator force limits in rodent.xml.

- This model has a bunch of ranges defined (tendon length ranges and actuator force-limit ranges) that are actually inactive due to the associated "limited" property not being set to "true".
- A recent change in MuJoCo enabled automatically inferring the "limited" property according to the presence of the associated "range" property, which changed the behaviour of this model and helped us realise the above situation.
- This CL explicitly disables tendon ranges limits and actuator force limits while leaving the ranges in place, so the model behaviour remains unchanged.
- Since many of the numbers seem to be carefully calibrated, it might be worth investigating in the future whether the limits should actually be activated.

PiperOrigin-RevId: 468690429
Change-Id: Icd097a2cafe15e910bca71c5378bddcf3d92665a

Author: yuvaltassa

dm_control/locomotion/walkers/assets/rodent.xml

@@ -5,7 +5,8 @@
     <joint limited="true" solreflimit="0.01 1" solimplimit="0.99 0.9999 0" armature="6e-07" damping="0.001"/>
     <geom friction="0.7 0.005 0.0001" solref="0.005 1"/>
     <site group="3" rgba="0 0 1 1"/>
-    <general ctrllimited="true" ctrlrange="-1 1" gainprm="0.01"/>
+    <general ctrllimited="true" ctrlrange="-1 1" forcelimited="false" gainprm="0.01"/>
+    <tendon limited="false"/>
     <default class="bone">
       <geom contype="0" conaffinity="0" group="0" rgba="0.5 0.5 0.5 1" density="1100.0"/>
     </default>