Fix minor bug in petab importer

[arrjon]

The Petab importer also generates an Amici model, which requires adapting parameter scales. However, a small bug occurred due to passing the entire dictionary to the rescale function instead of just the specific dictionary value. This resulted in failure during simulation.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.32%. Comparing base (6446a77) to head (d486ede).
Report is 236 commits behind head on develop.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #636      +/-   ##
===========================================
+ Coverage    84.08%   84.32%   +0.23%     
===========================================
  Files           91      141      +50     
  Lines         5260     8535    +3275     
===========================================
+ Hits          4423     7197    +2774     
- Misses         837     1338     +501     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.