Doc: Fix broken links to Qt docs

The Qt for MCU docs are currently not available online

Change-Id: I705f78b32c7723a29653b0407306406eee1a76a4
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

doc/src/mcu/creator-mcu-dev.qdoc

@@ -31,7 +31,7 @@
 
     \title Connecting MCUs
 
-    \l{Qt for MCU} enables you to use subsets of QML and Qt Quick Controls
+    Qt for MCU enables you to use subsets of QML and Qt Quick Controls
     to create user interfaces for devices that are powered by microcontroller
     units (MCU). It includes a new graphics rendering engine that has a low
     memory footprint and is optimized for MCUs and other resource-constrained

doc/src/projects/creator-only/creator-projects-settings-build.qdoc

@@ -183,7 +183,7 @@
     Since Qt 5.11, you can compile QML source code into the final binary. This
     improves the startup time of the application and eliminates the need to
     deploy QML files together with the application. For more information, see
-    \l{Compiling QML Ahead of Time}.
+    \l{Ahead-of-Time Compilation}.
 
     \QC new project wizards create Qt Quick projects that can be compiled,
     because they are set up to use the Qt Resource System. To compile Qt Quick

doc/src/qtquick/qtquick-profiler.qdoc

@@ -342,8 +342,8 @@
 
     In order to understand the scene graph category, it's important to
     understand how the Qt Quick scene graph works. See
-    \l {Qt Quick Scene Graph} and \l {Qt Quick Scene Graph Renderer} for a
-    detailed description. The following events are reported in the
+    \l {Qt Quick Scene Graph} and \l {Qt Quick Scene Graph Default Renderer}
+    for a detailed description. The following events are reported in the
     \uicontrol {Scene Graph} category. Not all events are generated by all render
     loops. In the Windows and Basic render loops everything runs in the same
     thread and the distinction between GUI thread and render thread is