Removing .set_title() from initial sns.heatmap call in display_heatmap.py

[Treece-Burgess]

Within the columnar index section of code, it was discussed previously to add a title automatically to the generated plot to distinguish what column index you were using to create the heatmap.

The original implementation for this was: sns.heatmap(thicket, columns, **kwargs).set_title('Title'). However, the issue with this implementation is that instead of returning axes that a user could change, it would return text and would not allow a user any way to change the plot.

The new implementation is the following:

ax = sns.heatmap(thicket, columns, **kwargs)
ax.set_title('Title')
return ax

This will still allow the functionality of setting the title, but also allow a user to change x and y ticks/labels.