🔥 Remove superheaters fouling

[pierre-eliep-met]

Goal

Superheaters fouling is not really a fault that happens on nuclear plants, because it is steam on both sides. It is an old REX from TVA. So I just removed the variable, not that it is a breaking change for previous faulty models 😬

Type of change

• [ ] Bugfix
• [ ] New feature
• [x] Refactoring change
• [ ] Release & Version Update (don't forget to change the version number in package.mo)

Will it break anything in previous models ?

• [x] Breaking change (If yes, make sure to point it out in the changelog)
• [ ] Non-Breaking change

Checklist

• [x] I have added the appropriate tags, reviewers, projects (and detailed the size and priority of my PR) and linked issues to this PR
• [x] I have performed a self-review of my own code
• [x] I have checked that all existing tests pass
• [ ] I have checked that my work is compatible with OpenModelica
• [x] I have added/updated tests that prove my development works and does not break anything.
• [ ] I have made corresponding changes or additions to the documentation (in Notion documentation)
• [ ] I have added corresponding entries to the Changelog
• [x] I have checked for conflicts with target branch, and merged/rebased in consequence

You can also fill these out after creating the PR, but make sure to check them all before submitting your PR for review.

[pierre-eliep-met]

(tiny PR to use a bit of extra time before the daily before my vacation 😇)