Fix pynews config in example file

The python news cog relies on the python_news section of the config being filled in via a named alias. Since we were using the DEV_ prefix, this meant it was not being populated, leading to the cog throwing an error on boot.

Author: ChrisLovering

pydis_site/apps/content/resources/guides/pydis-guides/contributing/bot.md

@@ -350,7 +350,7 @@ style:
 
         trashcan: "<:trashcan:�>"
 
-##### <<  Optional - If you don't care about the filtering and help channel cogs, ignore the rest of this file  >> #####
+##### <<  Optional - If you don't care about the filtering, help channel and py-news cogs, ignore the rest of this file  >> #####
 filter:
     # What do we filter?
     filter_domains:        true
@@ -426,6 +426,10 @@ help_channels:
     notify_roles:
         - *HELPERS_ROLE
 
+python_news:
+    channel: *DEV_PY_NEWS
+    webhook: *PYNEWS_WEBHOOK
+
 ##### <<  Add any additional sections you need to override from config-default.yml  >> #####
             </code>
           </pre>