Consistent ordering and formatting for talk events

Use a consistent format for talk events, with the most recent talk at
the top of the list with the rest in a descending order.

This removes the need to use a `reverse` filter in the events partial.

source/_talks/upgrading-your-site-drupal-9.md

@@ -11,22 +11,17 @@ video:
   type: youtube
   id: AcYMXiom0o8
 events:
-  - name: DrupalNYC
-    location: New York, USA
-    url: https://ti.to/drupalnyc/meetup-2020-09-02
-    date: 2020-09-02
+  -
+    name: Midwest PHP
+    url: https://midwestphp.org/talks/7C0m4I87vq72cDoXvsHFRp/Upgrading_your_site_to_Drupal_9
+    date: 2021-04-22
     online: true
-
-  - name: Leeds PHP
+  -
+    name: Leeds PHP
     location: Leeds, UK
     url: https://www.meetup.com/leedsphp/events/272504993
     date: 2020-09-23
     online: true
-
-  - name: Midwest PHP
-    url: https://midwestphp.org/talks/7C0m4I87vq72cDoXvsHFRp/Upgrading_your_site_to_Drupal_9
-    date: 2021-04-22
-    online: true
 ---
 
 For most Drupal Developers and users, the idea of moving a project from one