usb: linux/usb.h: fix Excess kernel-doc description warning

Remove the @removable: line to prevent the kernel-doc warning:

include/linux/usb.h:732: warning: Excess struct member 'removable' description in 'usb_device'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Link: https://lore.kernel.org/r/20231223050636.14022-1-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>