[Rules] Hyperlint Automation: Meta Description Fixes (#20437)

* PCX review
* Re-add empty line

---------

Co-authored-by: hyperlint-ai[bot] <154288675+hyperlint-ai[bot]@users.noreply.github.com>
Co-authored-by: Pedro Sousa <[email protected]>

Author: hyperlint-ai[bot]

src/content/docs/rules/transform/request-header-modification/index.mdx

@@ -6,6 +6,7 @@ sidebar:
 head:
   - tag: title
     content: HTTP request header modification rules
+description: Learn how to modify HTTP request headers with Cloudflare's rules.
 ---
 
 import { Render } from "~/components";