Remove rtm_type_name()

It has been unused since 2009 when Ken decided that the routing log
messages were too verbose (commit 91fc077c96926dd60).

(back ported from bcc91c8d8b3d5b775cfde1ee461d7e0394070852)

https://github.com/krb5/krb5/commit/d12a558d155e97cfbe3c6a48bf4a7f0559eefef0
Author: Ben Kaduk <kaduk@mit.edu>
Committer: Tom Yu <tlyu@mit.edu>
Commit: d12a558d155e97cfbe3c6a48bf4a7f0559eefef0
Branch: krb5-1.12
 src/lib/apputils/net-server.c |   35 -----------------------------------
 1 files changed, 0 insertions(+), 35 deletions(-)