refactor: use HfApi instead of Repository for hub sync

[Ashutosh0x]

Description: Refactor hub synchronization to use HfApi

This PR addresses #503 by refactoring the .github/hub/push_evaluations_to_hub.py script to use the modern huggingface_hub.HfApi instead of the legacy huggingface_hub.Repository class.

Key Changes

• Removed Git Dependency: By switching to HfApi.upload_folder and HfApi.create_tag, we eliminate the need for a local git clone and the overhead of managing a local Git repository.
• Improved Performance: Using HfApi is generally faster and more reliable than shell-based Git operations, especially in CI environments.
• Cleaner Implementation: Replaced ~40 lines of subprocess calls and manual Git handling with a concise tempfile.TemporaryDirectory and HfApi call.
• Simplified Dependency Management: The script now focuses purely on uploading the evaluation modules.

Benefits

• No more "Could not clone" errors due to environment/shell quirks.
• Reduced memory and disk footprint during CI execution.
• Aligning with the current best practices of the huggingface_hub ecosystem.

Fixes #503