docs: update screenshot for fields/rich-text (#14979)

Updates the screenshot to use lexical instead of slate.

Before: https://payloadcms.com/docs/fields/rich-text
After:
https://payloadcms.com/docs/dynamic/fields/rich-text?branch=AlessioGr-patch-1

Author: AlessioGr

docs/fields/rich-text.mdx

@@ -12,13 +12,12 @@ Consistent with Payload's goal of making you learn as little of Payload as possi
 
 Instead, you can invest your time and effort into learning the underlying open-source tools that will allow you to apply your learnings elsewhere as well.
 
-<LightDarkImage
-  alt="Shows a Rich Text field in the Payload Admin Panel"
+<PayloadMedia
+  mediaID="69444ac1cca4069327f4fad2"
   caption="Admin Panel screenshot of a Rich Text field"
-  srcDark="https://payloadcms.com/images/docs/fields/richtext-dark.png"
-  srcLight="https://payloadcms.com/images/docs/fields/richtext.png"
 />
 
+
 ## Config Options
 
 | Option                 | Description                                                                                                                                                                                                                                                                                             |