xdg-shell: recommend against drawing decorations when tiled

Port the changes made in 31236887 ("xdg-shell: move maximized
state definition together") to the various tiled states.

Signed-off-by: Simon Ser <contact@emersion.fr>

stable/xdg-shell/xdg-shell.xml

@@ -873,24 +873,36 @@
 	<description summary="the surface’s left edge is tiled">
 	  The window is currently in a tiled layout and the left edge is
 	  considered to be adjacent to another part of the tiling grid.
+
+	  The client should draw without shadow or other decoration outside of
+	  the window geometry on the left edge.
 	</description>
       </entry>
       <entry name="tiled_right" value="6" since="2">
 	<description summary="the surface’s right edge is tiled">
 	  The window is currently in a tiled layout and the right edge is
 	  considered to be adjacent to another part of the tiling grid.
+
+	  The client should draw without shadow or other decoration outside of
+	  the window geometry on the right edge.
 	</description>
       </entry>
       <entry name="tiled_top" value="7" since="2">
 	<description summary="the surface’s top edge is tiled">
 	  The window is currently in a tiled layout and the top edge is
 	  considered to be adjacent to another part of the tiling grid.
+
+	  The client should draw without shadow or other decoration outside of
+	  the window geometry on the top edge.
 	</description>
       </entry>
       <entry name="tiled_bottom" value="8" since="2">
 	<description summary="the surface’s bottom edge is tiled">
 	  The window is currently in a tiled layout and the bottom edge is
 	  considered to be adjacent to another part of the tiling grid.
+
+	  The client should draw without shadow or other decoration outside of
+	  the window geometry on the bottom edge.
 	</description>
       </entry>
       <entry name="suspended" value="9" since="6">