Fix problem with get_anomalies_prediction_interval

[ostreech1997]

Before submitting (must do checklist)

• Did you read the contribution guide?
• Did you update the docs? We use Numpy format for all the methods and classes.
• Did you write any new necessary tests?
• Did you update the CHANGELOG?

Proposed Changes

Closing issues

Closes #1280.

[codecov-commenter]

Codecov Report

Merging #1296 (199e496) into master (3f4ce91) will decrease coverage by 32.63%.
The diff coverage is 17.64%.

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@@             Coverage Diff             @@
##           master    #1296       +/-   ##
===========================================
- Coverage   88.75%   56.12%   -32.63%     
===========================================
  Files         193      193               
  Lines       11743    11746        +3     
===========================================
- Hits        10423     6593     -3830     
- Misses       1320     5153     +3833     

Impacted Files	Coverage Δ
.../analysis/outliers/prediction_interval_outliers.py	28.57% <17.64%> (-62.61%)	⬇️

... and 121 files with indirect coverage changes

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[github-actions]

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[Mr-Geekman]

Look at comments above.