Since we don't have different environment variables for the plugin paths,
users have to set QT_PLUGIN_PATH to where plugins for both Qt 5 and 6
(and future versions) are located. This causes Qt to print warnings that
those couldn't be loaded because the major version mismatches. So don't
print them any more.
QT_DEBUG_PLUGINS and the category logging filter can still be used to
enable them.
Fixes: QTBUG-107459
Pick-to: 6.5
Change-Id: Idd5e1bb52be047d7b4fffffd175318ca1f8017bd
Reviewed-by: Lars Knoll <lars@knoll.priv.no>
25e13c9079