Docs/fix trainer fct notebooks

[carlocagnetta]

• I have added the correct label(s) to this Pull Request or linked the relevant issue(s)
• I have provided a description of the changes in this Pull Request
• I have added documentation for my changes
• If applicable, I have added tests to cover my changes.
• I have reformatted the code using poe format
• I have checked style and types with poe lint and poe type-check
• (Optional) I ran tests locally with poe test
  (or a subset of them with poe test-reduced) ,and they pass
• (Optional) I have tested that documentation builds correctly with poe doc-build

This PR resolves #1008

[carlocagnetta]

@opcode81 This is the PR for the issue we discussed today
@MischaPanch Could you please review it?
I also changed a minor thing in the .rst files of the docu to upgrade to CarPole-v1

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ea48cc2) 88.06% compared to head (0fc4e9d) 88.06%.

❗ Current head 0fc4e9d differs from pull request most recent head a96b13c. Consider uploading reports for the commit a96b13c to get more accurate results

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1009   +/-   ##
=======================================
  Coverage   88.06%   88.06%           
=======================================
  Files          96       96           
  Lines        7531     7531           
=======================================
  Hits         6632     6632           
  Misses        899      899           

Flag	Coverage Δ
unittests	88.06% <ø> (ø)

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[MischaPanch]

The build fails because you committed a different python version to the notebook metadata. Could you undo this pls?

[MischaPanch]

The build on windows fails, but it has nothing to do with the changes here. Seems some caching problem in CI. If it appears on master, I'm gonna solve it in a separate PR. Merging this, thanks for the docs fixes!