remove django 2.2 from docs index (#8982)

Author: deronnax

docs/index.md

@@ -86,7 +86,7 @@ continued development by **[signing up for a paid plan][funding]**.
 REST framework requires the following:
 
 * Python (3.6, 3.7, 3.8, 3.9, 3.10, 3.11)
-* Django (2.2, 3.0, 3.1, 3.2, 4.0, 4.1)
+* Django (3.0, 3.1, 3.2, 4.0, 4.1)
 
 We **highly recommend** and only officially support the latest patch release of
 each Python and Django series.