Doc: update qml module version to 5.5.

And remove import statements from snippets.

Change-Id: I109beabd445186f96f0750b6f23fb623c125181e
Task-number: QTBUG-47620
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>

src/qtmultimediaquicktools/qdeclarativevideooutput.cpp

@@ -58,11 +58,7 @@ Q_LOGGING_CATEGORY(qLcVideo, "qt.multimedia.video")
     \ingroup multimedia_video_qml
     \inqmlmodule QtMultimedia
 
-    \c VideoOutput is part of the \b{QtMultimedia 5.0} module.
-
     \qml
-    import QtQuick 2.0
-    import QtMultimedia 5.0
 
     Rectangle {
         width: 800