DOC: Updated links to 2 tutorials in tutorials.rst

[tommyod]

Two of the links to the pandas-cookbook did not work for version v0.2 of the documents. Now all links work. Where a version v0.2 exists, it links to that version. In the remaining two cases, it now links to version v0.1 instead of raising the 404: Page not found error.

[jorisvandenbossche]

I would rather update the actual links and keep linking to the newer version, as those chapters still exist (the name was a bit changed): http://nbviewer.jupyter.org/github/jvns/pandas-cookbook/tree/master/cookbook/

[codecov]

Codecov Report

Merging #19857 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #19857   +/-   ##
=======================================
  Coverage   91.64%   91.64%           
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  Files         150      150           
  Lines       48946    48946           
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  Hits        44858    44858           
  Misses       4088     4088

Flag	Coverage Δ
#multiple	90.02% <ø> (ø)	⬆️
#single	41.81% <ø> (ø)	⬆️

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[tommyod]

I agree @jorisvandenbossche. Thanks for reviewing! I have updated this PR:

• Every link is to v2.0 now.
• Another chapter has been written (Chapter 9), I have added it.

And I believe this PR is good to go then.

[jreback]

thanks!