Add pagination to graphql queries in `platform.GetLatestApprovers()`

### TL;DR

Context in PR: https://github.com/abcxyz/guardian/pull/397#discussion_r1733527628

### Detailed design

_No response_

### Alternatives considered

_No response_

### Additional information

_No response_

Review the linked PR discussion to understand the context for adding pagination to the `platform.GetLatestApprovers()` GraphQL queries. Locate the function in the codebase, examine the existing query structure, and identify how pagination parameters (like limit/offset or cursors) should be integrated. Determine what 'done' looks like by checking if there are existing pagination patterns in the project's GraphQL implementation.

索引モデルが issue の本文から書いたものです。