Fix Travis 2.0

Summary: Missed another place where we had a float num contours .

Reviewed By: ldworkin

Differential Revision: D17052058

fbshipit-source-id: b446ae8af5b5767621e0d25ef80390cc17dfa93a

Author: lena-kashtelyan

ax/plot/helper.py

@@ -480,7 +480,7 @@ def contour_config_to_trace(config):
         "autocontour": True,
         "contours": {"coloring": "heatmap"},
         "hoverinfo": "x+y+z",
-        "ncontours": density / 2,
+        "ncontours": int(density / 2),
         "type": "contour",
         "x": grid_x,
         "y": grid_y,