Remove extra 'response' from comment

The word 'response' is typed twice in row in one of the comments. Remove
one of them to make the sentence sound right.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>
Don't user header name in exit message

Last-Modified is the name of the header, but it doesn't sound right when
written like that in the exit message. Change it so that it says that
the last modification was $diff seconds ago.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>