[AudioEngine] Minor improvement to the docu snippets

Without mentioning the playType property, it is unclear for the user
not familiar with AudioEngine why there are several PlayVariation-s
binded to a single Sound element.
Also fix a simply typo.

Change-Id: Ie6b4bff759318c70c94e75797cc6991cb9b918ca
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>

src/imports/audioengine/qdeclarative_playvariation_p.cpp

@@ -81,13 +81,14 @@ QT_USE_NAMESPACE
 
             Sound {
                 name:"explosion"
+                playType: Sound.Random
                 PlayVariation {
                     sample:"explosion01"
                     minPitch: 0.8
                     maxPitch: 1.1
                 }
                 PlayVariation {
-                    sample:"explosion01"
+                    sample:"explosion02"
                     minGain: 1.1
                     maxGain: 1.5
                 }

src/imports/audioengine/qdeclarative_sound_p.cpp

@@ -169,13 +169,14 @@ void QDeclarativeSoundCone::componentComplete()
 
             Sound {
                 name:"explosion"
+                playType: Sound.Random
                 PlayVariation {
                     sample:"explosion01"
                     minPitch: 0.8
                     maxPitch: 1.1
                 }
                 PlayVariation {
-                    sample:"explosion01"
+                    sample:"explosion02"
                     minGain: 1.1
                     maxGain: 1.5
                 }