Silence some deprecation warnings from finger.py.

PiperOrigin-RevId: 620038603
Change-Id: Ib7bf0d712d324f17efdfe3ade053782659570b43

Author: nimrod-gileadi

dm_control/suite/finger.py

@@ -90,7 +90,7 @@ def touch(self):
 
   def hinge_velocity(self):
     """Returns the velocity of the hinge joint."""
-    return self.named.data.sensordata['hinge_velocity']
+    return self.named.data.sensordata['hinge_velocity'][0]
 
   def tip_position(self):
     """Returns the (x,z) position of the tip relative to the hinge."""