xdg-shell: Remove "edges" from description

The parameter was dropped...
diff --git a/protocol/xdg-shell.xml b/protocol/xdg-shell.xml
index ef755b7..3fb4b0c 100644
--- a/protocol/xdg-shell.xml
+++ b/protocol/xdg-shell.xml
@@ -249,12 +249,6 @@
 	ignore it if it doesn't resize, pick a smaller size (to
 	satisfy aspect ratio or resize in steps of NxM pixels).
 
-	The edges parameter provides a hint about how the surface
-	was resized. The client may use this information to decide
-	how to adjust its content to the new size (e.g. a scrolling
-	area might adjust its content position to leave the viewable
-	content unmoved). Valid edge values are from resize_edge enum.
-
 	The client is free to dismiss all but the last configure
 	event it received.