Update the version to 2026.09 (#374)

Author: renetapopova

antora.yml

@@ -1,14 +1,14 @@
 name: java-reference
 title: Java Reference
-version: '2026.08'
+version: '2026.09'
 start_page: ROOT:index.adoc
 nav:
 - modules/ROOT/content-nav.adoc
 asciidoc:
   attributes:
-    neo4j-version: '2026.08'
-    neo4j-version-exact: '2026.08.0'
-    neo4j-buildnumber: '2026.08'
+    neo4j-version: '2026.09'
+    neo4j-version-exact: '2026.09.0'
+    neo4j-buildnumber: '2026.09'
     java-driver-version: '6.2.1'
     neo4j-documentation-branch: 'dev'
     page-origin-private: false