`create_figure` Returns the Figure

[itsdawei]

Description

Simplify confusing code in visualizer.show(). Turns out we don't use t_heatmaps anywhere.

Status

• [x] I have read the guidelines in CONTRIBUTING.md
• [x] I have formatted my code using yapf
• [x] I have linted my code with pylint
• [x] I have tested my code by running pytest
• [x] I have added a one-line description of my change to the changelog in HISTORY.md
• [x] This PR is ready to go