Improve the warning message about legacy validation key reg
Improve the warning message about legacy validation key reg

It's the legacy method. Call it that and maybe people will stop using it.

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

gene1wood/chef,chef/chef,higanworks/chef,jaymzh/chef,tas50/chef-1,mwrock/chef,higanworks/chef,nvwls/chef,MsysTechnologiesllc/chef,mattray/chef,mattray/chef,nvwls/chef,chef/chef,jaymzh/chef,tas50/chef-1,mwrock/chef,nvwls/chef,mattray/chef,tas50/chef-1,mwrock/chef,MsysTechnologiesllc/chef,nvwls/chef,tas50/chef-1,mwrock/chef,MsysTechnologiesllc/chef,chef/chef,jaymzh/chef,MsysTechnologiesllc/chef,gene1wood/chef,higanworks/chef,jaymzh/chef,nvwls/chef,higanworks/chef,mattray/chef,mattray/chef,higanworks/chef,gene1wood/chef,nvwls/chef,gene1wood/chef,chef/chef