cursor-channel: Remove obsolete size check

In the past CursorItem structure was stored in
RedCursorCmd::device_data field so the check was there to check if the
structure fit into that field.
Since 2ba69f9f88
("libspice: add surface 0 support") the structure is no more stored in
the field so there's no reason for this check causing only confusion.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Acked-by: Victor Toso <victortoso@redhat.com>

server/cursor-channel.c

@@ -34,8 +34,6 @@ typedef struct CursorItem {
     RedCursorCmd *red_cursor;
 } CursorItem;
 
-G_STATIC_ASSERT(sizeof(CursorItem) <= QXL_CURSUR_DEVICE_DATA_SIZE);
-
 struct CursorChannel
 {
     CommonGraphicsChannel parent;