Fix typo in 2.2.0 release vignette (#2683)

rentangle -> rectangle

Author: jemus42

vignettes/releases/ggplot2-2.2.0.Rmd

@@ -73,7 +73,7 @@ The facet and layout implementation has been moved to ggproto and received a lar
     ```
 
 *   Axes are now drawn under the panels in `facet_wrap()` when the 
-    rentangle is not completely filled.
+    rectangle is not completely filled.
     
     ```{r facet-2}
     ggplot(mpg, aes(displ, hwy)) +