Refocus particle surface tests (#4076)

Author: gdaviet

newton/tests/test_examples.py

@@ -980,7 +980,7 @@ class TestMPMExamples(unittest.TestCase):
         "num-frames": 10,
         "voxel-size": 0.15,
         "surface-voxel-size": 0.075,
-        "surface-max-grid-cells": 4_000_000,
+        "surface-max-grid-cells": 300_000,
         "particles-per-cell": 1,
         "world-count": 2,
     },