docs: Do not include from drivers/scsi/constants.c

The only function of interest in that file was scsi_print_status().  That
function was removed in commit 7ac70763 (scsi: remove
scsi_print_status()) but the docs were not changed to match, yielding this
warning:

    ./drivers/scsi/constants.c:1: warning: no structured comments found

There's nothing there anymore, so just remove that section from the docs.
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/driver-api/scsi.rst

@@ -224,14 +224,6 @@ mid to lowlevel SCSI driver interface
 .. kernel-doc:: drivers/scsi/hosts.c
    :export:
 
-drivers/scsi/constants.c
-~~~~~~~~~~~~~~~~~~~~~~~~
-
-mid to lowlevel SCSI driver interface
-
-.. kernel-doc:: drivers/scsi/constants.c
-   :export:
-
 Transport classes
 -----------------