Fix artifacts when hovering over reference images in HiDPI mode

Thanks Freya Lupen for the provided patch!

BUG:441216


(cherry picked from commit 213f967e)

libs/ui/opengl/kis_opengl_canvas2.cpp

@@ -200,7 +200,7 @@ void KisOpenGLCanvas2::paintGL()
     {
         QPainter gc(this);
         if (!updateRect.isEmpty()) {
-            gc.setClipRect(updateRect);
+            gc.setClipRect(kisGrowRect(updateRect, 1));
         }
 
         QRect decorationsBoundingRect = coordinatesConverter()->imageRectInWidgetPixels().toAlignedRect();