Add note clarifying Java versions for Vector index performance suggestions (#1225)

Author: JPryce-Aklundh

modules/ROOT/pages/indexes/semantic-indexes/vector-indexes.adoc

@@ -256,7 +256,7 @@ Use xref:functions/vector.adoc[] to compute the similarity score between two spe
 [[performance]]
 == Performance suggestions
 
-Vector indexes can take advantage of the incubated Java 20 Vector API for noticeable speed improvements.
+Vector indexes can take advantage of the incubated Java Vector API for noticeable speed improvements.
 If you are using a compatible version of Java, you can add the following setting to your link:{neo4j-docs-base-uri}/operations-manual/current/configuration/configuration-settings/#config_server.jvm.additional[configuration settings]:
 
 .Configuration settings
@@ -265,6 +265,11 @@ If you are using a compatible version of Java, you can add the following setting
 server.jvm.additional=--add-modules=jdk.incubator.vector
 ----
 
+[NOTE]
+While the Neo4j 5 series requires at least Java 17, _at least_ Java 20 is necessary to take advantage of this performance improvement in Neo4j 5.14-5.26.
+If you are using Neo4j 2025.01 or later, Java 21 is required.
+For more information about what Java versions are supported by different Neo4j versions, see the link:{neo4j-docs-base-uri}/operations-manual/current/installation/requirements/#deployment-requirements-java[Operations Manual -> System requirements -> Java].
+
 [[show-vector-indexes]]
 == Show vector indexes