Defining multiple primary_key constraints at the column level is not supported

[will-sargent-dbtlabs]

What are you changing in this pull request and why?

Revises the verbiage based on a recent conversation with the core team, where multiple column-level primary key constraints actually fails silently in 1.7, but will generate a warning in 1.8 as unsupported.

We are not clear about this today in docs, leading to potential confusion and technical debt for users on older versions.

Checklist

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

Adding or removing pages (delete if not applicable):

• Add/remove page in website/sidebars.js
• Provide a unique filename for new pages
• Add an entry for deleted pages in website/vercel.json
• Run link testing locally with npm run build to update the links that point to deleted pages

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
docs-getdbt-com	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 4, 2024 9:41am

[dbeatty10]

See dbt-labs/dbt-bigquery#1016 (comment) where a user ran into this (and here where we responded with an example).