Regression testing not running on catalysis example

[rwest]

There was an effort in PR #2470 to get the RMS_liquidSurface_ch4o2cat regression testing working.
It was paused until #2335 could be merged, which got some surface diff methods working.
In commit 77cf7f4 as part of #2473 we instead modified the continuous integration to not bother trying to compare RMS_liquidSurface_ch4o2cat, because we were blocked, figuring that at least we would detect if running it crashed.

This issue is a reminder that we intended to fix RMS_liquidSurface_ch4o2cat, once #2335 was working (which it now is) and properly run the regression comparison.

Clarification: I think a surface example is run, and even the models are compared now, it's just the observables testing that is missing. (?)

[github-actions]

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