Fixed AndroidManifest.xml syntax in Android camerapreview sample

samples/android/tutorial-1-camerapreview/gradle/AndroidManifest.xml

@@ -26,13 +26,13 @@
                       android:largeScreens="true"
                       android:anyDensity="true" />
 
-    //! [camera_permissions]
+    <!--[camera_permissions]-->
     <uses-permission android:name="android.permission.CAMERA"/>
 
     <uses-feature android:name="android.hardware.camera" android:required="false"/>
     <uses-feature android:name="android.hardware.camera.autofocus" android:required="false"/>
     <uses-feature android:name="android.hardware.camera.front" android:required="false"/>
     <uses-feature android:name="android.hardware.camera.front.autofocus" android:required="false"/>
-    //! [camera_permissions]
+    <!--[camera_permissions]-->
 
 </manifest>