Remove reused CHANGES entry

Remove reused CHANGES entry

Changes entry 6063 was added to the v9_18 branch (by commit
cb3990001fb2ce978a44cc9d03b679cf626d03b1) without an associated
placeholder in the main branch.  The same entry number was subsequently
reused for a different change in the main branch (by commit
41870dccbae3872154d5a6a76d70b5cb40d82c05).  To prevent confusion, remove
the entry from the v9_18 branch as the original code change whose
reversal is mentioned in entry 6063 was not accompanied by its own
CHANGES entry.