Fix typo in Next.js App Router preparation document

[jbluemink]

Description / Motivation

Corrected a typo in the word 'applicaiton' to 'application'.

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update (non-breaking change; modified files are limited to the /data directory or other markdown files)

Checklist:

• I have read the Contributing guide.
• My code/comments/docs fully adhere to the Code of Conduct.
• My change is a code change.
• My change is a documentation change and there are NO other updates required.
• My change has new or updated images which are stored in the /public/images folder that need to be migrated to Sitecore DAM

[vercel]

@jbluemink is attempting to deploy a commit to the Sitecore Technical Marketing Team on Vercel.

A member of the Team first needs to authorize it.