Update heatmaps.md

doc/python/heatmaps.md

@@ -102,7 +102,7 @@ fig.show()
 
 ### Heatmap with Categorical Axis Labels
 
-In this example we also show how to ignore [hovertext](https://plotly.com/python/hover-text-and-formatting/) when we have [missing values](https://plotly.com/python/missing_values) in the data by setting the [hoverongaps](https://plotly.com/python/reference/heatmap/#heatmap-hoverongaps) to False.
+In this example we also show how to ignore [hovertext](https://plotly.com/python/hover-text-and-formatting/) when we have missing values in the data by setting the [hoverongaps](https://plotly.com/python/reference/heatmap/#heatmap-hoverongaps) to False.
 
 ```python
 import plotly.graph_objects as go