refactor: remove `/api/v1/validators` endpoint

[mvadari]

High Level Overview of Change

This PR removes the /api/v1/validators endpoint, and instead has the frontend directly call the VHS. All it was doing was caching, basically.

Context of Change

Simplifying the Explorer codebase.

Type of Change

• [x] Refactor (non-breaking change that only restructures code)

TypeScript/Hooks Update

• [ ] Updated files to React Hooks
• [ ] Updated files to TypeScript

Before / After

N/A

Test Plan

CI passes.

Future Tasks

Update the VHS API to cache better/maybe even provide this exact API.