CPP12 — Remnant of read-only return values and out params

About two or three years ago, we decided to deprecate the read-only
nature of in params on the server side, and out params and return values
on the client side.

The second-last para of 1.13.2 still contains a remnant that we forgot
to clean up back then:

As with other out and return values, out and return sequences must
not be assigned to by the caller without first copying them.

I would suggest to modify this sentence to read:

For a sequence passed to an operation as an in parameter, the
operation must not assign to the sequence if its release flag
is false and the sequence has variable-length elements.

For a sequence passed to a client as an out parameter or return
value, the client must not assign to the sequence if its
release flag is false and the sequence has variable-length elements.

This captures more correctly the intent and the semantics of the release
flag (because assigning to a sequence with the release flag set to true
is perfectly OK).

see below