Bump ci-queue from 0.20.8 to 0.21.0 (#1210)

Bumps [ci-queue](https://github.com/Shopify/ci-queue) from 0.20.8 to 0.21.0.
- [Release notes](https://github.com/Shopify/ci-queue/releases)
- [Commits](Shopify/ci-queue@v0.20.8...v0.21.0)

---
updated-dependencies:
- dependency-name: ci-queue
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -1,7 +1,7 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    ci-queue (0.20.8)
+    ci-queue (0.21.0)
     citrus (3.0.2)
     diff-lcs (1.4.4)
     erubis (2.7.0)