Fix channel trigger variable type when the trigger is automatically detected

[smoia]

Closes #

This PR fixes a bug that appears when slice4phys interacts with automatic trigger detection.
Before, automatic rigger detection was not forcing the trigger channel number variable to be an integer. This PR changes that.

Proposed Changes

Change Type

• bugfix (+0.0.1)
• minor (+0.1.0)
• major (+1.0.0)
• refactoring (no version update)
• test (no version update)
• infrastructure (no version update)
• documentation (no version update)
• other

Checklist before review

• I added everything I wanted to add to this PR.
• [Code or tests only] I wrote/updated the necessary docstrings.
• [Code or tests only] I ran and passed tests locally.
• [Documentation only] I built the docs locally.
• My contribution is harmonious with the rest of the code: I'm not introducing repetitions.
• My code respects the adopted style, especially linting conventions.
• The title of this PR is explanatory on its own, enough to be understood as part of a changelog.
• I added or indicated the right labels.

• I added information regarding the timeline of completion for this PR.

• Please, comment on my PR while it's a draft and give me feedback on the development!

[codecov]

Codecov Report

Merging #440 (1032c09) into master (ba981ee) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #440      +/-   ##
==========================================
+ Coverage   94.82%   94.83%   +0.01%     
==========================================
  Files           8        8              
  Lines         966      968       +2     
==========================================
+ Hits          916      918       +2     
  Misses         50       50              

Impacted Files	Coverage Δ
phys2bids/physio_obj.py	94.09% <100.00%> (+0.05%)	⬆️

[smoia]

🚀 PR was released in 2.8.2 🚀