Modify blog/rss plugin config to make search work again

Inheriting config for mkdocs requires that you use key/value pairs for the
plugins not a list of objects.

mkdocs-online.yml

@@ -5,15 +5,15 @@ site_url: https://textual.textualize.io/
 edit_uri: edit/main/docs/
 
 plugins:
-  - blog:
-  - rss:
-      match_path: blog/posts/.*
-      date_from_meta:
-        as_creation: date
-      categories:
-        - categories
-        - release
-        - tags
+  blog:
+  rss:
+    match_path: blog/posts/.*
+    date_from_meta:
+      as_creation: date
+    categories:
+      - categories
+      - release
+      - tags
 
 nav:
   - Introduction: