Update model-contracts.md for supported models

[nathangriffiths-cdx]

What are you changing in this pull request and why?

Update to show that incremental models with on_schema_change: fail are actually supported (only on_schema_change: append_new_columns is mentioned but this was changed here dbt-labs/dbt-core#8006)

Reformatted the list to make it clearer what is and isn't supported.

Checklist

• Review the Content style guide and About versioning so my content adheres to these guidelines.
• Add a checklist item for anything that needs to happen before this PR is merged, such as "needs technical review" or "change base branch."

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Name	Status	Preview	Comments	Updated (UTC)
docs-getdbt-com	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jan 8, 2024 11:25am

[welcome]

Hello!👋 Thanks for contributing to the dbt product documentation and opening this pull request! ✨
We use Markdown and some HTML to write the dbt product documentation. When writing content, you can use our style guide and content types to understand our writing standards and how we organize information in the dbt product docs.
We'll review your contribution and respond as soon as we can. 😄

[matthewshaver]

Thank you @nathangriffiths-cdx Made some minor alterations based on style guide but this is a nice improvement and we appreciate it.