[Dev Plat] Update playwright.mdx (#22651)

Let's emphasise this product is in beta.

Author: nenizera

src/content/docs/browser-rendering/platform/playwright.mdx

@@ -1,6 +1,6 @@
 ---
 pcx_content_type: concept
-title: Playwright
+title: Playwright (beta)
 description: Learn how to use Playwright with Cloudflare Workers for browser automation. Access Playwright API, manage sessions, and optimize browser rendering.
 sidebar:
   order: 5