Update usage-stats.md

[runleonarun]

Closes #6707

What are you changing in this pull request and why?

Fixed usage stats page to use dbt project for the global config flag

Checklist

• I have reviewed the Content style guide so my content adheres to these guidelines.
• The topic I'm writing about is for specific dbt version(s) and I have versioned it according to the version a whole page and/or version a block of content guidelines.
• I have added checklist item(s) to this list for anything anything that needs to happen before this PR is merged, such as "needs technical review" or "change base branch."
• The content in this PR requires a dbt release note, so I added one to the release notes page.

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🚀 Deployment available! Here are the direct links to the updated files:

• https://docs-getdbt-com-git-runleonarun-patch-15-dbt-labs.vercel.app/reference/global-configs/usage-stats

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[mirnawong1]

lgtm!