Improve uv download action

[JerryChen97]

Try fixing recent torch downloading issue by constraining our concurrent download threads as well as increase timeout.

  UV_CONCURRENT_DOWNLOADS: 1
  UV_HTTP_TIMEOUT: 120

Reference: https://docs.astral.sh/uv/reference/environment/

[sc-122720]

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.46%. Comparing base (f189a97) to head (d7ac561).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9696   +/-   ##
=======================================
  Coverage   99.46%   99.46%           
=======================================
  Files         628      628           
  Lines       68882    68882           
=======================================
  Hits        68516    68516           
  Misses        366      366           

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