Don't set Desktop singleton L&F in AUv3Synth plug-in example

examples/Plugins/AUv3SynthPluginDemo.h

@@ -187,7 +187,7 @@ public:
         : AudioProcessorEditor (processorIn),
           roomSizeSlider (Slider::LinearHorizontal, Slider::NoTextBox)
     {
-        LookAndFeel::setDefaultLookAndFeel (&materialLookAndFeel);
+        setLookAndFeel (&materialLookAndFeel);
 
         roomSizeSlider.setValue (getParameterValue ("roomSize"), NotificationType::dontSendNotification);
 
@@ -213,6 +213,11 @@ public:
         startTimer (100);
     }
 
+    ~AUv3SynthEditor() override
+    {
+        setLookAndFeel (nullptr);
+    }
+
     //==============================================================================
     void paint (Graphics& g) override
     {