Contract init: add flag removal message

[Ifropc]

What

We plan to remove some flags from contract init as part of breaking changes (see #1586). This PR does just that.
Removed argument are hidden from help:

And when trying to use them there's an error that explains what are the alternatives.

error: invalid value 'test' for '--with-example <WITH_EXAMPLE>': This argument has been removed and will be not be recognized by the future versions of CLI: Adding examples via cli is no longer supported. You can still clone examples from the repo https://github.com/stellar/soroban-examples

For more information, try '--help'.

Why

See above

Known limitations

N/A