Fix typo in deprecation warning supression docs

[mmansikka]

Fix typo in Upcoming Deprecation warning

What are you changing in this pull request and why?

The error name in docs is wrong and creates a compilation error. This typo fix resolves this issue and there is no compilation error. Check here for what name is expected (UpcomingReferenceDeprecation) vs. what is in the docs (UpcomingDeprecationReference)

Checklist

• [x ] I have reviewed the Content style guide so my content adheres to these guidelines.
• [x ] 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.
• [x ] 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."

[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.
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[mirnawong1]

hey @mmansikka , great catch! thanks so much for opening this pr up to fix this - I'll go ahead and get this merged. really looking forward to any future contributions ✨ !