Fix typo in ui-controls.asc

Fix typo "iv3 and iv3 are" to "iv2 and iv3 are" in the ui-controls.asc file

src/docs/asciidoc/ui-controls.asc

@@ -919,7 +919,7 @@ ImageView is a Node container that allows the Image object to be used in JavaFX
         iv4.setViewport(viewportRect);
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-iv3 and iv3 are based on the image2 and image3 objects.  Recall that these objects produced transformed images that fit the square container.
+iv2 and iv3 are based on the image2 and image3 objects.  Recall that these objects produced transformed images that fit the square container.
 
 iv4 is also based on a transformed Image object, but in the case of iv4, the transformation is done through the ImageView object rather than the Image.  ImageView.setFitHeight is called rather than Image.setFitHeight.