update thedescription of the CI test matrix

docs/modules/ROOT/pages/release.adoc

@@ -33,7 +33,7 @@ workflow to run at GitHub Actions.
 The workflow is defined by
 https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/.github/workflows/main.yml[the "main.yml" script].
 It performs clean builds of the Engine
-across a matrix of 4 operating systems and 2 Java versions.
+across a matrix of 3 operating systems and 3 Java versions.
 It also performs a clean build of the merged javadoc.
 
 Any failure of the CI workflow causes notifications to be sent.