Fix readout pulses for drag_simple with unrolling

[andrea-pasquale]

As title says.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.87%. Comparing base (8ba2b5b) to head (2db28bd).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1219      +/-   ##
==========================================
- Coverage   97.90%   97.87%   -0.03%     
==========================================
  Files         131      131              
  Lines       10034    10034              
==========================================
- Hits         9824     9821       -3     
- Misses        210      213       +3     

Flag	Coverage Δ
unittests	97.87% <ø> (-0.03%)	⬇️

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Files with missing lines	Coverage Δ
src/qibocal/protocols/drag/drag_simple.py	100.00% <ø> (ø)

... and 3 files with indirect coverage changes

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[Luca-Ben-Herrmann]

I confirm that this fixes the bug.