docs: note that 'featured date' field is unused (#1058)

## Overview

Note that the "Featured date" field is not used.

## Related

- [RT #38551](https://tickets.tacc.utexas.edu/Ticket/Display.html?id=38551)

## Changes

- **changed** "Featured date" to "Featured date (unused)"

## Testing & UI

| before | after |
| - | - |
| <img width="385" height="470" alt="before"
src="https://github.com/user-attachments/assets/09ba0b6f-03db-419d-9291-df79480b8ece"
/> | <img width="385" height="470" alt="after"
src="https://github.com/user-attachments/assets/8126d8f8-d561-4b79-b2e1-5900b4078fab"
/> |

Author: wesleyboar

taccsite_cms/locale/en/LC_MESSAGES/django.mo

@@ -99,6 +99,11 @@ msgstr ""
 "created post. "
 "And any post that unsets its size will use this size."
 
+#: djangocms-blog
+#: https://github.com/nephila/djangocms-blog/blob/2.0.3/djangocms_blog/locale/en/LC_MESSAGES/django.po#L426-L428
+msgid "featured date"
+msgstr "featured date (unused)"
+
 #: djangocms-blog
 #: https://github.com/nephila/djangocms-blog/blob/2.0.3/djangocms_blog/locale/en/LC_MESSAGES/django.po#L688-L690
 # this link text only appears for a CMS editor