Update incorrect comment (nerfstudio-project#1226)

nerfstudio/models/instant_ngp.py

@@ -66,7 +66,7 @@ class InstantNGPModelConfig(ModelConfig):
     grid_resolution: int = 128
     """Resolution of the grid used for the field."""
     contraction_type: ContractionType = ContractionType.UN_BOUNDED_SPHERE
-    """Resolution of the grid used for the field."""
+    """Contraction type used for spatial deformation of the field."""
     cone_angle: float = 0.004
     """Should be set to 0.0 for blender scenes but 1./256 for real scenes."""
     render_step_size: float = 0.01