Update login.py - ARGILLA_CACHE_DIR environment variable

[7flash]

• [x] Improvement (change adding some improvement to an existing functionality)

I think sometimes it's important to be able provide custom path for cache directory, particularly in my case since it's running in runpod container with limited container storage, I must provide a path to cache directory in mounted volume, otherwise when running argilla login I get error OSError: [Errno 28] No space left on device: '/root/.cache/argilla'