[Docs] Fix documentation site build failures

[adamziel]

Motivation for the change, related issues

Removes the two HTML comments with HTML code snippets in them to fix the following docs site build error:

Error: MDX compilation failed for file "/home/runner/work/wordpress-playground/wordpress-playground/packages/docs/site/i18n/es/docusaurus-plugin-content-docs/current/main/guides/for-plugin-developers.md"
Cause: Unexpected character `!` (U+0021) before name, expected a character that can start a name, such as a letter, `$`, or `_` (note: to create a comment in MDX, use `{/* text */}`)
Details:

It must have fell through the cracks in one of the recent translation PRs based on an older version of trunk that did not yet have docs site e2e tests.

cc @fellyph