Remove antiquated \since lines in docs.

They aren't useful in the case of QtMultimedia{Kit}

Change-Id: If1b0b6625763c85907fb05beb9c440046472ddef
Reviewed-by: Jonas Rabbe <jonas.rabbe@nokia.com>

src/imports/multimedia/qdeclarativecamera.cpp

@@ -70,7 +70,6 @@ void QDeclarativeCamera::_q_updateState(QCamera::State state)
 
 /*!
     \qmlclass Camera QDeclarativeCamera
-    \since 4.7
     \brief The Camera element allows you to add camera viewfinder to a scene.
     \ingroup qml-multimedia
     \inherits Item

src/imports/multimedia/qdeclarativecameraexposure.cpp

@@ -46,7 +46,6 @@ QT_BEGIN_NAMESPACE
 
 /*!
     \qmlclass CameraExposure QDeclarativeCameraExposure
-    \since 5.0
     \brief The CameraExposure element provides interface for exposure related camera settings.
     \ingroup qml-multimedia
 

src/imports/multimedia/qdeclarativecameraflash.cpp

@@ -46,7 +46,6 @@ QT_BEGIN_NAMESPACE
 
 /*!
     \qmlclass CameraFlash QDeclarativeCameraFlash
-    \since 5.0
     \brief The CameraFlash element provides interface for flash related camera settings.
     \ingroup qml-multimedia
 

src/imports/multimedia/qdeclarativecamerafocus.cpp

@@ -46,7 +46,6 @@ QT_BEGIN_NAMESPACE
 
 /*!
     \qmlclass CameraFocus QDeclarativeCameraFocus
-    \since 5.0
     \brief The CameraFocus element provides interface for focus related camera settings.
     \ingroup qml-multimedia
 

src/imports/multimedia/qdeclarativeradio.cpp

@@ -45,7 +45,6 @@ QT_BEGIN_NAMESPACE
 
 /*!
     \qmlclass Radio QDeclarativeRadio
-    \since 5.0.0
     \brief The Radio element allows you to access radio functionality from a QML application.
     \ingroup qml-multimedia
     \inherits Item

src/imports/multimedia/qdeclarativeradiodata.cpp

@@ -45,7 +45,6 @@ QT_BEGIN_NAMESPACE
 
 /*!
     \qmlclass RadioData QDeclarativeRadioData
-    \since 5.0.0
     \brief The RadioData element allows you to access RDS data from a QML application.
     \ingroup qml-multimedia
     \inherits Item

src/imports/multimedia/qdeclarativevideooutput.cpp

@@ -118,7 +118,6 @@ private:
 /*!
     \qmlclass VideoOutput QDeclarativeVideoOutput
     \brief The VideoOutput element allows you to render video or camera viewfinder.
-    \since 5.0.0
 
     \ingroup qml-multimedia