fix: improve embedding documentation to use encoders

[eugeniosegala]

Description of change

Updating embedding documentation to prioritise native encoders.

Pull-Request Checklist

• Code is up-to-date with the master branch
• npm run format to apply eslint formatting
• npm run test passes with this change
• Documentation has been updated to reflect this change
• The new commits and pull request title follow conventions explained in pull request guidelines (PRs that do not follow this convention will not be merged)

[giladgd]

Thanks for the PR!
I don't think that a comment inside a code example is the right place to guide on choosing the right embedding model.
I've opened PR #396 to enhance the Choosing a Model guide to include a paragraph about embedding models.