[Task]: Update google-cloud-spanner to 6.85.0

[jrmccluskey]

What needs to happen?

Update the google-cloud-spanner client to 6.85.0 for the beam 2.63.0 release.

https://cloud.google.com/java/docs/reference/google-cloud-spanner/latest/overview

https://github.com/googleapis/java-cloud-bom?tab=readme-ov-file#libraries-bom-v26530

Issue Priority

Priority: 2 (default / most normal work should be filed as P2)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam YAML
• Component: Beam examples
• Component: Beam playground
• Component: Beam katas
• Component: Website
• Component: Infrastructure
• Component: Spark Runner
• Component: Flink Runner
• Component: Samza Runner
• Component: Twister2 Runner
• Component: Hazelcast Jet Runner
• Component: Google Cloud Dataflow Runner

[jrmccluskey]

Done in #33682