Update variants.yml path to mozilla-firefox/firefox repository

[Copilot]

Summary

This PR updates the variants.yml file path to point to the new location in the mozilla-firefox/firefox repository on GitHub, as the file has been moved from its previous location in mozilla-central.

Changes

Updated three constants in bugbot/rules/variant_expiration.py:

1. VARIANTS_PATH: Changed from taskcluster/kinds/test/variants.yml to taskcluster/test_configs/variants.yml

2. VARIANTS_URL (renamed from VARIANTS_HG_URL): Changed from the Mercurial URL to the new GitHub raw URL:

   • Old: https://hg.mozilla.org/mozilla-central/raw-file/tip/taskcluster/kinds/test/variants.yml
   • New: https://raw.githubusercontent.com/mozilla-firefox/firefox/refs/heads/main/taskcluster/test_configs/variants.yml

3. VARIANTS_SEARCHFOX_URL: Updated to use the new path while keeping the searchfox.org domain:

   • Old: https://searchfox.org/mozilla-central/source/taskcluster/kinds/test/variants.yml
   • New: https://searchfox.org/mozilla-central/source/taskcluster/test_configs/variants.yml

Impact

• The get_variants() method will now fetch variants from the new GitHub location
• Bug descriptions and comments will continue to link to Searchfox with the updated path
• All existing functionality is preserved; only the data source location has changed
• No breaking changes to the API or behavior

Testing

• ✅ Verified VARIANTS_URL is accessible (HTTP 200)
• ✅ Confirmed YAML parsing works correctly (34 variants found)
• ✅ Passed ruff linting and formatting checks
• ✅ CodeQL security scan: 0 vulnerabilities detected

Fixes the issue where the old Mercurial URL was no longer accessible after the repository migration.

[!WARNING]

Original prompt

---

This section details on the original issue you should resolve

<filter_complete></filter_complete>

<issue_title>Change the path for the variants.yml file to be retrived from mozilla-firefox/firefox</issue_title>
<issue_description>The new path seems to be https://raw.githubusercontent.com/mozilla-firefox/firefox/refs/heads/main/taskcluster/test_configs/variants.yml</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #2747

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Change the path for the variants.yml file to be retrived from mozilla-firefox/firefox</issue_title>
<issue_description>The new path seems to be https://raw.githubusercontent.com/mozilla-firefox/firefox/refs/heads/main/taskcluster/test_configs/variants.yml</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #2747

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[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• searchfox.org
  • Triggering command: curl -s -o /dev/null -w %{http_code} REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)