Update vector-index-memory-configuration.adoc

I think we mean that the machine must have sufficient memory. Saying OS could be confused with the OS memory we say Lucene requires.

Author: mauvo

modules/ROOT/pages/performance/vector-index-memory-configuration.adoc

@@ -3,7 +3,7 @@
 
 Vector indexes are based on link:https://lucene.apache.org/[Lucene].
 Lucene does not Neo4j page cache memory, it uses OS memory as described in the xref:performance/memory-configuration.adoc[Memory configuration] section.
-When you have a vector index, you must ensure that the OS has sufficient memory for the JVM heap, Neo4j page cache, and the Lucene vector indexes to perform optimally.
+When you have a vector index, you must ensure that there is sufficient memory for the JVM heap, Neo4j page cache, and the Lucene vector indexes to perform optimally.
 If Lucene has insufficient memory, the OS will perform page swapping and read data from disk, which will dramatically degrade the Neo4j vector index search performance.
 Tools like IOTOP can assist in understanding disk I/O usage.
 
@@ -25,6 +25,8 @@ In the event of a rolling restart/patch/upgrade, an approach may be needed to ad
 
 == Optimal Neo4j memory configuration for vector indexes
 
+
+
 The memory configuration recommendations are _Heap + Neo4j PageCache + .25(Vector Index Size) + Additional OS Managed Memory_.