update flame_wave He inputs

[zingale]

PR summary

This adds a non-square inputs file with a cooler He layer, which produces a nicely defined flame (in 2-d). This will be the basis for a new 3-d run. This also cleans up some of the older inputs files.

PR motivation

PR checklist

• [ ] test suite needs to be run on this PR
• [ ] this PR will change answers in the test suite to more than roundoff level
• [ ] all newly-added functions have docstrings as per the coding conventions
• [ ] the CHANGES file has been updated, if appropriate
• [ ] if appropriate, this change is described in the docs