fix: improve description and correct plot for ‘auto’ correlation

[jtook]

No description provided.

[aquemy]

@fabclmnt the other examples are in python while this one is a Notebook. I am OK with that, and the example if fine to me but I just want to check with you that we can allow Notebooks as examples in the future.

[fabclmnt]

@jtook this is not a feat it is at maximum a fix because you included changes at the level of the correlation.py file.

As examples are out of the package they should not be considered for version increment of the package. Can you please change the PR message in accordance?
Also, can you please confirm the license of the dataset used?

@aquemy as this is for the feature folder and not for the use-cases folder, I'll ask to have this changed to a python file. The change is minor and it eases the consumption of the code to generate automated documentation, as we have in other examples.

Notebooks should be used for examples such as usaairquality or employees-chicago.

[codecov-commenter]

Codecov Report

Base: 90.95% // Head: 90.95% // No change to project coverage 👍

Coverage data is based on head (dc97941) compared to base (06ec172).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1119   +/-   ##
========================================
  Coverage    90.95%   90.95%           
========================================
  Files          179      179           
  Lines         5084     5084           
========================================
  Hits          4624     4624           
  Misses         460      460           

Flag	Coverage Δ
py3.8-ubuntu-latest-pandas	90.95% <100.00%> (ø)

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

Impacted Files	Coverage Δ
.../pandas_profiling/report/structure/correlations.py	96.42% <100.00%> (ø)

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[jtook]

The changes you requested have been made. I used a dataset that is already being used in the examples folder from the UCI dataset collection

I verified the changes with James