Docs: Move form-text paragraph to Form control page

[hannahiss]

Move form-text paragraph to Form control page instead of overview to have the documentation in the same page than sass variables.

Description

Motivation & Context

Documentation of form-text and list of sass variables are not in the same page in the documentation:

• form-text documentation: https://getbootstrap.com/docs/5.3/forms/overview/#form-text
• variables documentation: https://getbootstrap.com/docs/5.3/forms/form-control/#sass-variables

This PR is a proposal to move form-text in Form control page, but we could also move form-text variables to Overview page...

Type of changes

• Refactoring (non-breaking change)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Live previews

• https://deploy-preview-37871--twbs-bootstrap.netlify.app/docs/5.3/forms/form-control/

Related issues

[mdo]

I can dig, thanks!