add release notes to 6.4.0
#### <sub><sup><a name="5390" href="#5390">:link:</a></sup></sub> feature
* Add `--team` flag for `fly set-pipelines` command #5805
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+#### <sub><sup><a name="5830" href="#5830">:link:</a></sup></sub> fix
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+* Fix a validation issue where a step can be set with 0 attempts causing the ATC to panic. #5830
