Hotfix for minus sign in DRAG shape

[stavros11]

Fixes #826. We were originally planning to postpone this to 0.2, where it is automatically fixed, however since it is relevant for some experiments done now (see https://github.com/qiboteam/qibocal/pull/689#issuecomment-2041002106) and the fix was easy, it would be good to merge it now.

I repeated the experiments from https://github.com/qiboteam/qibocal/pull/689#pullrequestreview-1982457594 using Sergi's runcards from the reports uploaded in that comment before and after DRAG calibration. Here are my reports after the sign correction:

Before: http://login.qrccluster.com:9000/2LXRRtnlTV-dnJXpxoN7BQ== After: http://login.qrccluster.com:9000/Ov8k7evxSfuy7GburXvBiQ==

The difference is small, but I believe DRAG now works more consistently over all qubits (in contrast to before that was only working for qubit 0 for which beta > 0). @igres26 @andrea-pasquale you can also confirm if you like.

(@alecandido maybe you can double check the fix - it is only one line but it's in regex which, as you know, is my favorite!)

[codecov[bot]]

Codecov Report

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

Project coverage is 66.67%. Comparing base (4ae5445) to head (c6945e6).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #869 +/- ## ======================================= Coverage 66.67% 66.67% ======================================= Files 55 55 Lines 5902 5902 ======================================= Hits 3935 3935 Misses 1967 1967 ``` | [Flag](https://app.codecov.io/gh/qiboteam/qibolab/pull/869/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/qiboteam/qibolab/pull/869/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | `66.67% <100.00%> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam#carryforward-flags-in-the-pull-request-comment) to find out more.

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[alecandido]

Given that this is a temporary patch, and only thought to work for the cases we have at hand, I will leave the approval to actual "users" (i.e. @igres26 and @andrea-pasquale)

[alecandido]

Thanks @andrea-pasquale and @igres26, I have no further comment.

@stavros11, you can proceed merging!