And expand the note in the openglwindow example to point to
hellogles3 as well.
Change-Id: I2c0ee9b83fa59752d937c57eaf0194f0d0a8a7d9
Reviewed-by: Christian Strømme <christian.stromme@qt.io>
(cherry picked from commit 7c23aa6bc5e5d7b6e891fb0c30a72091a60c79eb)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>