Update hardcoded vaadin version to 23.6.2 (#4504)

Co-authored-by: Zhe Sun <31067185+ZheSun88@users.noreply.github.com>

Author: vaadin-bot

articles/_vaadin-version.adoc

@@ -1 +1 @@
-:vaadin-version: 23.6.0
+:vaadin-version: 23.6.2