docs(tree): update stories to csf3 for Training Tree component

[ncruz-av]

Before submitting a pull request, please make sure the following is done:

1. Fork the repository and create your branch from master.
2. Run yarn in the repository root.
3. If you've fixed a bug or added code that should be tested, add tests!
4. Ensure the test suite passes (yarn test). Tip: yarn test --watch TestName is helpful in development.
5. Make sure your code passed the conventional commits check. Read more about conventional commits

[codecov[bot]]

Codecov Report

Merging #1343 (6d0fc41) into master (973ca28) will increase coverage by 6.39%. Report is 1 commits behind head on master. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1343      +/-   ##
==========================================
+ Coverage   92.85%   99.25%   +6.39%     
==========================================
  Files          22        2      -20     
  Lines         504      267     -237     
  Branches      166       91      -75     
==========================================
- Hits          468      265     -203     
+ Misses         36        2      -34     

see 24 files with indirect coverage changes