My bad, I had other figures around and didn't realize the heatmap object is child of the figure, not of an axes on the figure as most other plot objects have historically been.
Your h2 variable is the handle to the heatmap object you created--it's already an object; use it as is, don't muck on it and make a struct out of it.
If you instead mean the actual cell labels, those apparently cannot be removed--altho don't know why one would want to:
Error using matlab.graphics.chart.HeatmapChart/set.YDisplayData
Empty strings and strings containing only space are invalid y values.
Guess one could change .FontColor color to figure background and would disappear visually...