chore: Upgrade to v25 api

[matthewmcneely]

Description

This is a DRAFT PR.

This PR upgrades pydgraph to support the new v25 gRPC API

Checklist

• Code compiles correctly and linting passes locally
• For all code changes, an entry added to the CHANGELOG.md file describing and linking to
  this PR
• Tests added for new functionality, or regression tests for bug fixes added as applicable
• For public APIs, new features, etc., PR on
  docs repo staged and linked here

[matthewmcneely]

Closing in favor of #277