Update api.en-US.mdx

[ryancole]

Without the hyphen it could mean a Promise that returns a function, as opposed to a function that returns a Promise.

Description

• [ ] Adding new page
• [X] Updating existing documentation
• [ ] Other updates

[vercel[bot]]

@ryancole is attempting to deploy a commit to the Vercel Team on Vercel.

A member of the Team first needs to authorize it.