remove frontmatter checking code to use new `frontmatter-check` pre-commit.

[kjaymiller]

In trying to standardize the blog post we added some frontmatter checking code that would be ran in pre-commit.

That code is standardized with https://github.com/kjaymiller/frontmatter-check.

• Remove the existing frontmatter checking code
• Change the pre-commit information over to the frontmatter-check recipe