Fix cmake and qmake instructions for widget items

Fixes: QTBUG-131366
Change-Id: I694cfe262e31593010bc03ac56748680e7996359
Reviewed-by: Alexei Cazacov <alexei.cazacov@qt.io>
Reviewed-by: Sami Varanka <sami.varanka@qt.io>
(cherry picked from commit 0a2ff2356f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit c0284da019)

src/doc/qtgraphs.qdoc

@@ -7,6 +7,12 @@
     \qtvariable graphs
 */
 
+/*!
+    \module QtGraphsWidgets
+    \qtcmakepackage GraphsWidgets
+    \qtvariable graphswidgets
+*/
+
 /*!
     \title Qt Graphs C++ Classes
     \group graphs

src/graphs3d/widget/q3dbarswidgetitem.cpp

@@ -9,7 +9,7 @@ QT_BEGIN_NAMESPACE
 
 /*!
  * \class Q3DBarsWidgetItem
- * \inmodule QtGraphs
+ * \inmodule QtGraphsWidgets
  * \ingroup graphs_3D_widgets
  * \brief The Q3DBarsWidgetItem class provides methods for rendering 3D bar graphs.
  *

src/graphs3d/widget/q3dgraphswidgetitem.cpp

@@ -15,7 +15,7 @@ QT_BEGIN_NAMESPACE
 
 /*!
  * \class Q3DGraphsWidgetItem
- * \inmodule QtGraphs
+ * \inmodule QtGraphsWidgets
  * \ingroup graphs_3D_widgets
  * \brief The Q3DGraphsWidgetItem class provides a window and render loop for
  * graphs.

src/graphs3d/widget/q3dscatterwidgetitem.cpp

@@ -9,7 +9,7 @@ QT_BEGIN_NAMESPACE
 
 /*!
  * \class Q3DScatterWidgetItem
- * \inmodule QtGraphs
+ * \inmodule QtGraphsWidgets
  * \ingroup graphs_3D_widgets
  * \brief The Q3DScatterWidgetItem class provides methods for rendering 3D scatter graphs.
  *

src/graphs3d/widget/q3dsurfacewidgetitem.cpp

@@ -9,7 +9,7 @@ QT_BEGIN_NAMESPACE
 
 /*!
  * \class Q3DSurfaceWidgetItem
- * \inmodule QtGraphs
+ * \inmodule QtGraphsWidgets
  * \ingroup graphs_3D_widgets
  * \brief The Q3DSurfaceWidgetItem class provides methods for rendering 3D surface plots.
  *