Add upgrade note about dropping Jinja2 2.x support

docs/releases/3.0.md

@@ -62,7 +62,7 @@ class LandingPage(Page):
  * Avoid an unnecessary page reload when pressing enter within the header search bar (Images, Pages, Documents) (Riley de Mestre)
  * Removed unofficial length parameter on `If-Modified-Since` header in `sendfile_streaming_backend` which was only used by IE (Mariusz Felisiak)
  * Add Pinterest support to the list of default oEmbed providers (Dharmik Gangani)
- * Update Jinja2 template support for Jinja2 3.x (Seb Brown)
+ * Update Jinja2 template support for Jinja2 3.1 (Seb Brown)
  * Add ability for `StreamField` to use `JSONField` to store data, rather than `TextField` (Sage Abdullah)
  * Split up linting / formatting tasks in Makefile into client and server components (Hitansh Shah)
  * Add support for embedding Instagram reels (Luis Nell)
@@ -111,7 +111,6 @@ wagtail updatemodulepaths --diff  # show the changes to be made, without updatin
 wagtail updatemodulepaths  # actually update the files
 ```
 
-
 ### Removed warning in Internet Explorer (IE11)
 
 * IE11 support was officially dropped in Wagtail 2.15, as of this release there will no longer be a warning shown to users of this browser.
@@ -203,3 +202,7 @@ After setting the keyword argument, make sure to generate and run the migrations
 -   See [](wagtailadmin_base_url).
 -   `BASE_URL` was not documented but it provides a way to configure the base URL for the Wagtail admin which is used mostly in notifications.
 -    Usage of `BASE_URL` will be removed in a future release and it is recommended that the you update the setting in this release.
+
+### Removed support for Jinja2 2.x
+
+Jinja2 2.x is no longer supported as of this release; if you are using Jinja2 templating on your project, please upgrade to Jinja2 3.0 or above.