Increase image golden test tolerance.

This accounts for the difference between swrast and llvmpipe software rendering drivers from Mesa.

PiperOrigin-RevId: 570365527
Change-Id: I2b4d072c384a7056ba59f6fab6654d2c7310f160

Author: saran-t

dm_control/mujoco/testing/image_utils.py

@@ -203,7 +203,7 @@ def compute_rms(image1, image2):
   return np.sqrt(float(sum_of_squares) / abs_diff.size)
 
 
-def assert_images_close(expected, actual, tolerance=10.):
+def assert_images_close(expected, actual, tolerance=23.5):
   """Tests whether two images are almost equal.
 
   Args: