Fix CREATE EXTERNAL TABLE syntax

[moshap-firebolt]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context.

When should this PR be released to the public?

If the feature is live, the docs can be scheduled for immediate release by filing the PR to the gh-pages branch.
If it's part of a future release, please file the PR against the correcsponding release/packdb- branch.

Documentation Checklist

• I've previewed my documentation locally running make start-local (or using this tutorial)
• I've validated that indexing works and that I'm able to navigate to the documentation page from the table of contents
• If I added SQL examples, I have validated that they run correctly and as described.

If this PR touches a function implementation (aggregate, scalar, or table-valued):

• I've made sure my documentation is aligned with these guidelines on function documentation
• I've validated that the parent of my docs page is set correctly and the function shows up in the right category of the table of contents
• I've made sure that the function was added to the function glossary

[github-actions]

$\color{green}{\text{👍 Link Check Status: SUCCESS}}$