Bump erlef/setup-beam from 1.20.2 to 1.21.0 (#582)

Bumps [erlef/setup-beam](https://github.com/erlef/setup-beam) from 1.20.2 to 1.21.0.
- [Release notes](https://github.com/erlef/setup-beam/releases)
- [Commits](erlef/setup-beam@6389fe5...3580539)

---
updated-dependencies:
- dependency-name: erlef/setup-beam
  dependency-version: 1.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.github/workflows/test.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3
 
-      - uses: erlef/setup-beam@6389fe58dcb1ee91fd829c7c65bf8771b06dacc4
+      - uses: erlef/setup-beam@3580539ceec3dc05b0ed51e9e10b08eb7a7c2bb4
         with:
           otp-version: "26.2"
           gleam-version: "1.10.0"