update regression test files for old intrinsic models

I added regression tests a while ago testing if older pet files that only saved parameters of one model were still correctly loaded, but probably while updating the version of the pet file the test files also got the new syntax, effectively making the tests pointless. So I reversed the changes and remade the pet files in the old version and syntax.

Reviewer Checklist

General code quality

• naming conventions are met (see .clang-tidy for detailed information)
• no static analyzer warnings in new code parts (e.g., use clang-tidy for checking)

General usability

• old versions of pet-files are still loadable
• documentation updated (if applicable)

Only if changes in UI

• new elements are also saved and loaded from pet-file
• check if tab order is still correct
• all new SpinBoxes are promoted
• new keybindings added to Petrack::keyBindings()

Closes #516 (closed)