[Fix] Signal_fixpeaks_neurokit

[pfilo8]

This PR aims at repairing a possible bug in the _signal_fixpeaks_neurokit method from the signal_fixpeaks method, i.e., the wrong argument is passed to the _interpolate_big function.

Another night - another catch!

Proposed Changes

One-line change which is self-explanatory.

Checklist

Here are some things to check before creating the PR. If you encounter any issues, do let us know :)

• I have read the CONTRIBUTING file.
• My PR is targetted at the dev branch (and not towards the master branch).
• I ran the CODE CHECKS on the files I added or modified and fixed the errors.
• I have added the newly added features to News.rst (if applicable)

[welcome]

Thanks for opening this pull request! We'll make sure it's perfect before merging 🤗
Make sure to read the contributing guide. Also, if you think that your contribution is worthy of it, you can consider adding yourself to the Contributors list (feel free to ask us if you have any doubts).

[codecov-commenter]

Codecov Report

Merging #538 (acc2ecc) into dev (c110438) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev     #538      +/-   ##
==========================================
+ Coverage   85.31%   85.37%   +0.06%     
==========================================
  Files         199      199              
  Lines        9750     9772      +22     
==========================================
+ Hits         8318     8343      +25     
+ Misses       1432     1429       -3     

Impacted Files	Coverage Δ
neurokit2/signal/signal_fixpeaks.py	97.70% <100.00%> (ø)
neurokit2/complexity/entropy_multiscale.py	94.23% <0.00%> (-1.12%)	⬇️
neurokit2/complexity/fractal_katz.py	100.00% <0.00%> (ø)
neurokit2/complexity/entropy_fuzzy.py	100.00% <0.00%> (ø)
neurokit2/complexity/entropy_sample.py	100.00% <0.00%> (ø)
neurokit2/complexity/entropy_shannon.py	100.00% <0.00%> (ø)
neurokit2/complexity/fractal_higuchi.py	94.89% <0.00%> (+0.05%)	⬆️
neurokit2/emg/emg_activation.py	87.32% <0.00%> (+0.08%)	⬆️
neurokit2/complexity/fractal_dfa.py	93.33% <0.00%> (+0.09%)	⬆️
neurokit2/complexity/complexity_lempelziv.py	95.34% <0.00%> (+0.11%)	⬆️
... and 5 more

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[DominiqueMakowski]

Awesome, thanks again! feel free to add yourself to the contributors list :)