btl/sm: remove the deprecation-notice shell

The SM BTL was effectively removed a long time ago.  All that was left
was a shell that warned people if they tried to use the SM BTL.  For
v5.0, we plan to finally remove this ancient shell (and possibly
replace it with vader).

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>

Author: jsquyres