Fix invalid prop in example

Author: mbohal

src/lib/components/Button/README.mdx

@@ -245,7 +245,7 @@ Badges play nicely with icon buttons, too:
   />
   <Button
     label="Icon button with badge"
-    labelVisibility="desktop"
+    labelVisibility="md"
     priority="outline"
     beforeLabel={<Icon icon="warning-sign" />}
     startCorner={<Badge label={3} color="danger" />}