Fix 404 issue with the reference docs

Due to an antora ordering issue, the reference docs on the latest GA from
the project site throws an HTTP 404.

See spring-projects/spring-framework#32083 for more details.

src/reference/antora/antora-playbook.yml

@@ -1,10 +1,11 @@
 antora:
   extensions:
     - '@springio/antora-extensions/partial-build-extension'
+    - # atlas-extension must be before latest-version-extension so the latest versions are applied to imported versions
+    - '@antora/atlas-extension'
     - require: '@springio/antora-extensions/latest-version-extension'
     - require: '@springio/antora-extensions/inject-collector-cache-config-extension'
     - '@antora/collector-extension'
-    - '@antora/atlas-extension'
     - require: '@springio/antora-extensions/root-component-extension'
       root_component_name: 'amqp'
       # FIXME: Run antora once using this extension to migrate to the Asciidoc Tabs syntax