feat(spanner): add new change_stream.proto (#2315)

* feat(spanner): add new change_stream.proto PiperOrigin-RevId: 766241102 Source-Link: googleapis/googleapis@2bea1fc Source-Link: googleapis/googleapis-gen@f429e2a Copy-Tag: eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiZjQyOWUyYTg2NDkyZmUzNzc1NDA3OWZmMDIzNmNiYWMzYmUxYmZiYSJ9 * 🦉 Updates from OwlBot post-processor See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md --------- Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

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