mlx.4: Remove stale diagnostic message

This message would never have been omitted before since
bus_generic_attach never fails.

Reviewed by:	ziaee, emaste
Fixes:	18250ec6c0 Replace calls to bus_generic_attach with bus_attach_children
Differential Revision:	https://reviews.freebsd.org/D48402

share/man/man4/mlx.4

@@ -23,7 +23,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd February 15, 2017
+.Dd January 10, 2025
 .Dt MLX 4
 .Os
 .Sh NAME
@@ -146,7 +146,6 @@ controller.
 The current status of all system drives could not be fetched; attachment
 of system drives will be aborted.
 .It mlx%d: device_add_child failed
-.It mlx%d: bus_generic_attach returned %d
 .Pp
 Creation of the system drive instances failed; attachment of one or more
 system drives may have been aborted.