Fix plot scripts

[HansOlsson]

Closes #4316
I believe these make sense. I don't know exactly what they intended to show, but:

• wall and heater have somewhat similar heat-flows showing that you heat and it is lost in the wall later on
• in the other two cases there were already enough variables plotted in that diagram, so I don't think we need the extra one

[m-kessler]

Your changes are all fine.

However, the scripts are not very good and should have some general clean-up. But maybe this is another issue.

[beutlich]

However, the scripts are not very good and should have some general clean-up. But maybe this is another issue.

@casella Perhaps, MAP-Lib could spend some of its budget to convert the vendor-specific plot scripts to specified figure annotations.