docs: reword when to use model inputs

[andrewseguin]

PR Checklist

Please check if your PR fulfills the following requirements:

• [ ] The commit message follows our guidelines: https://github.com/angular/angular/blob/main/CONTRIBUTING.md#commit
• [ ] Tests for the changes have been added (for bug fixes / features)
• [x] Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• [ ] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [x] Documentation content changes
• [ ] angular.io application / infrastructure changes
• [ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

[JeanMeche]

@andrewseguin Could you squash the 2 commits, thank you !

[devversion]

This PR was merged into the repository by commit 1d18b075883965ad6a90d33ae45e08409c5f6ea0.

The changes were merged into the following branches: main, 18.2.x

[angular-automatic-lock-bot[bot]]

This issue has been automatically locked due to inactivity. Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}