Use zapier-style link markdown

[enkeboll]

What are you changing in this pull request and why?

This example code seems to want to embed a hyperlink using standard Slack-supported markdown, but apparently Zapier markdown is slightly different.

This is what it looked like before:

And with this change:

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."

[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. 😄

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[mirnawong1]

great catch, thanks so much @enkeboll ! appreciate you opening this pr up to fix this - looking forward to future contributions ✨