gl-renderer: Fix a typo in the output_set_border description

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>

src/gl-renderer.h

@@ -75,8 +75,8 @@ struct gl_renderer_interface {
 	 * tightly packed.
 	 *
 	 * The top and bottom textures will extend over the sides to the
-	 * full width of the bordered window while.  The right and left
+	 * full width of the bordered window.  The right and left edges,
-	 * edges, however, will extend only to the top and bottom of the
+	 * however, will extend only to the top and bottom of the
 	 * compositor surface.  This is demonstrated by the picture below:
 	 *
 	 * +-----------------------+