Fix 2 incorrect MD frontmatter entries

[2u841r]

Fixes #2173

• Show 610: removed linkedin: zachlloyd standalone key which is not part of the schema
• Show 616: changed url from an array to a single string https://nerdy.dev/, removing gradient.style

[vercel]

@2u841r is attempting to deploy a commit to the Syntax Team on Vercel.

A member of the Team first needs to authorize it.

[wesbos]

thanks a ton