Do not re-sort changes on their 'written on' timestamp

ChangeMessagesUtil#byChange(notes) already returns all change
messages in chronological order, oldest first. Moreover, sorting
change messages based on their 'written on' timestamp can produce
unexpected results when several messages are written at exactly
the same timestamp.

Change-Id: I9fbdffc9f48a9f113fc75169aa41a0c218c5cf39
1 file changed