Update Java driver version to 4.4.21 (#301)

Author: NataliaIvakina

antora.yml

@@ -11,4 +11,4 @@ asciidoc:
     neo4j-version: '4.4'
     neo4j-version-exact: '4.4.45'
     neo4j-buildnumber: '4.4'
-    java-driver-version: '4.4.20'
+    java-driver-version: '4.4.21'