feat: add mentions of Prisma Postgres and clear deprecated info

[ankur-arch]

This PR updates the v8.8 and canary docs to:

• Remove all references to the deprecated Prisma Data Proxy to clean up outdated documentation.
• Introduce mentions of Prisma Postgres to clarify available Postgres-based data workflows.
• Add guidance around Local Prisma Postgres to assist users in local development setups.

[Tobbe]

Thanks @ankur-arch. This is great!
Would you mind making the same changes to https://github.com/cedarjs/cedar?

[ankur-arch]

Thanks @Tobbe, I'll raise a PR within the next few days!