Combine references to Qt WebEngine submodules into one

Edit the description.

Change-Id: I3baf4725715738c19269ce857be6d5132ed1bdd6
Reviewed-by: Martin Smith <martin.smith@theqtcompany.com>

doc/src/qtmodules.qdoc

@@ -263,17 +263,8 @@
         \li \l[QtWebEngine]{Qt WebEngine}
         \li All
         \li \l{Qt for Windows}{Windows}, \l{Qt for Linux/X11}{Linux}, and \l{Qt for OS X}{OS X}.
-        \li Provides a QML API to run web applications using the \l{http://www.chromium.org/Home}{Chromium browser project}.
-    \row
-        \li \l[QtWebEngineWidgets]{Qt WebEngine Widgets}
-        \li All
-        \li \l{Qt for Windows}{Windows}, \l{Qt for Linux/X11}{Linux}, and \l{Qt for OS X}{OS X}.
-        \li Provides a C++ API to run web applications using the \l{http://www.chromium.org/Home}{Chromium browser project}.
-    \row
-        \li \l[QtWebEngineCore]{Qt WebEngine Core}
-        \li All
-        \li \l{Qt for Windows}{Windows}, \l{Qt for Linux/X11}{Linux}, and \l{Qt for OS X}{OS X}.
-        \li Provides a public API shared by both \l[QtWebEngine]{Qt WebEngine} and \l[QtWebEngineWidgets]{Qt WebEngine Widgets}.
+        \li Classes and functions for embedding web content in applications using the
+            \l{http://www.chromium.org/Home}{Chromium browser project}.
     \row
         \li \l[QtWebSockets]{Qt WebSockets}
         \li All