Fix changelog labels for storefront, i18n and legacy promotions

[jarednorman]

Summary

When solidus_storefront (#6468) and solidus_i18n (#6537) were merged into the monorepo, we forgot to update the PR labeler. PRs touching storefront/ or i18n/ have been falling through to the changelog:repository catch-all, which is why both merge PRs have that label.

While fixing that, I noticed that bin/release/update-release-draft only emits PRs whose label has a category
in .github/release.yml and silently drops the rest. changelog:solidus_legacy_promotions has never had a category, so legacy promotions PRs have been missing from generated release notes since that gem was split out. Between v4.6.2 and v4.7.0 alone, 8 PRs were dropped this way. It's a sad fate to be forgotten.

Checklist

Check out our PR guidelines for more details.

The following are mandatory for all PRs:

• I agree that my PR will be published under the same license as Solidus.
• I have written a thorough PR description.
• I have kept my commits small and atomic.
• I have localized any and all user-facing strings that I added to the source code.
• I have used clear, explanatory commit messages.

The following are not always needed:

• 📖 I have updated the README to account for my changes.
• 📑 I have documented new code with YARD.
• 🛣️ I have opened a PR to update the guides.
• ✅ I have added automated tests to cover my changes.
• 📸 I have attached screenshots to demo visual changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.26%. Comparing base (ebfaca3) to head (fb913b0).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6578   +/-   ##
=======================================
  Coverage   92.26%   92.26%           
=======================================
  Files        1037     1037           
  Lines       21228    21228           
=======================================
  Hits        19586    19586           
  Misses       1642     1642           

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[tvdeyen]

Great catch