Malformed code blocks in blog

[jorpic]

Describe the bug Several blog posts on getsynth.com are not very readable.

To Reproduce Steps to reproduce the behavior:

1. Navigate to the Seeding test databases blog post in your browser.

2. See error

Expected behavior Nicely rendered code block with colorful JSON in it.

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This was introduced in recent commit.

Apparently, docusaurus does not recognize this as a start of a code block due to backticks around date_time.

```json synth[expect = "unknown variant `date_time`"]

Possible solution could be to escape those backticks in markdown and unescape them back in doc tests.