Replace hardcoded bucket names with generic ones/env variables

[melissawm]

Description

Replaces some hardcoded GCS bucket names with generic ones, recommending using an env variable for that when reasonable.

Tests

Documentation builds correctly locally.

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• [N/A] I have performed a self-review of my code. For an optional AI review, add the gemini-review label.
• [N/A] I have necessary comments in my code, particularly in hard-to-understand areas.
• [N/A] I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed, including adding new documentation pages to the relevant Table of Contents (toctree directive) as explained in our documentation.

[melissawm]

The links being flagged as broken are actually the result of a rate-limit from huggingface. This will be fixed if we do less frequent broken link checks.