modified antora.yml and preview.yml for version 6

Author: rsill-neo4j

antora.yml

@@ -1,6 +1,7 @@
 name: graphql
 title: Neo4j GraphQL Library
-version: '5'
+version: '6'
+display_version: '6-beta'
 start_page: ROOT:index.adoc
 nav:
 - modules/ROOT/content-nav.adoc

preview.yml

@@ -24,7 +24,7 @@ urls:
 antora:
   extensions:
   - require: "@neo4j-antora/antora-modify-sitemaps"
-    sitemap_version: '5'
+    sitemap_version: '6'
     sitemap_loc_version: 'current'
     move_sitemaps_to_components: true
   - require: "@neo4j-antora/antora-page-list"