fix chevron for no couplers

[Jacfomg]

Checklist:

• Reviewers confirm new code works as expected.
• Tests are passing.
• Coverage does not decrease.
• Documentation is updated.
• Compatibility with Qibo modules (Please edit this section if the current pull request is not compatible with the following branches).
  • Qibo: master
  • Qibolab: couplers2
  • Qibolab_platforms_qrc: main

[codecov]

Codecov Report

Merging #591 (90e8670) into main (7893a8c) will decrease coverage by 0.05%.
Report is 5 commits behind head on main.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #591      +/-   ##
==========================================
- Coverage   96.05%   96.00%   -0.05%     
==========================================
  Files          92       92              
  Lines        6164     6165       +1     
==========================================
- Hits         5921     5919       -2     
- Misses        243      246       +3     

Flag	Coverage Δ
unittests	96.00% <100.00%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
.../characterization/two_qubit_interaction/chevron.py	97.70% <100.00%> (+0.01%)	⬆️

... and 1 file with indirect coverage changes

[andrea-pasquale]

Thanks @Jacfomg, LGTM and it works on qw5q_gold.