remove apparently unused system messages

Authored by MC8.


remove apparently unused system messages

This commit removes some system messages that appear to have been
removed in previous commits. For example, the characters remaining
message was removed in fc0e91aa1db91c2649438d4d074dbcc083e61f7f.

Note that I have not checked for the removal commit in all instances;
rather these do not appear if you grep for the keys within the current
revision. They certainly aren't used anywhere obvious.

Change-Id: I88755385623b889e9b55379f751c02232258572e