block/io: remove duplicate GLOBAL_STATE_CODE() in bdrv_do_drained_end()

block/io: remove duplicate GLOBAL_STATE_CODE() in bdrv_do_drained_end()

Both commit ab61335025 ("block: drain from main loop thread in
bdrv_co_yield_to_drain()") and commit d05ab380db ("block: Mark drain
related functions GRAPH_RDLOCK") introduced a GLOBAL_STATE_CODE()
macro in bdrv_do_drained_end(). The assertion of being in the main
thread cannot change here, so keep only the earlier instance.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-23-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>