Remove mentionings of kern.dumpdev which is no longer available.
Remove mentionings of kern.dumpdev which is no longer available.

PR:		docs/113570
Submitted by:	lawrance
MFC After:	3 days (where applicable)

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase