Docs: don't link to removed example

Change-Id: I5fcec02cd18971150eec4f119d902c695bf2ebb9
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Safiyyah Moosa <safiyyah.moosa@qt.io>
(cherry picked from commit 70f9158e0f046feba2d5b655a9b3fcc715d2e8be)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

examples/vulkan/doc/src/hellovulkantriangle.qdoc

@@ -8,9 +8,8 @@
     \title Hello Vulkan Triangle Example
     \brief Shows the basics of rendering with QVulkanWindow and the Vulkan API.
 
-    The \e{Hello Vulkan Triangle Example} builds on \l hellovulkanwindow. This
+    The \e{Hello Vulkan Triangle Example} creates a full graphics pipeline,
-    time a full graphics pipeline is created, including a vertex and fragment
+    including a vertex and fragment shader, to render a triangle.
-    shader. This pipeline is then used to render a triangle.
 
     \image hellovulkantriangle.png
 

src/gui/doc/src/qtgui-overview.qdoc

@@ -117,7 +117,7 @@
     \endlist
 
     For more information, see the \l{Hello Vulkan Widget Example}
-    and the \l {Hello Vulkan Window Example}.
+    and the \l {Hello Vulkan Triangle Example}.
 
     \section1 Drag and Drop