fix: explicitly convert parameter bounds to list of tuples

[alexander-held]

A bug fix in typeguard 4.2.0 started flagging a type inconsistency where model.config.suggested_bounds() contains elements that are lists instead of tuples with custom parameter bound configuration, see https://github.com/scikit-hep/pyhf/issues/2462. This fix here works around this by explicitly converting to a list of tuples for further use within cabinetry.

If the behavior in pyhf changes, this should be reverted / adjusted in the future.

* convert parameter bounds to list of tuples for consistent types when custom bounds are used

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (f116d4e) to head (768074e).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #471 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 22 22 Lines 2093 2093 Branches 344 346 +2 ========================================= Hits 2093 2093 ```

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