Fix version of `statsforecast` to 1.4 to avoid dependency conflicts during installation

[Mr-Geekman]

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?
• [x] Did you update the CHANGELOG?

Proposed Changes

Fix version of statsforecast to 1.4.

Closing issues

[github-actions[bot]]

🚀 Deployed on https://deploy-preview-1313--etna-docs.netlify.app

[codecov-commenter]

Codecov Report

Merging #1313 (a677361) into master (766d10b) will increase coverage by 0.14%. The diff coverage is n/a.

:exclamation: Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the Github App Integration for your organization. Read more.

@@            Coverage Diff             @@
##           master    #1313      +/-   ##
==========================================
+ Coverage   88.79%   88.94%   +0.14%     
==========================================
  Files         203      203              
  Lines       12461    12466       +5     
==========================================
+ Hits        11065    11088      +23     
+ Misses       1396     1378      -18     

see 7 files with indirect coverage changes

:mega: We’re building smart automated test selection to slash your CI/CD build times. Learn more