[skip-changelog] bump setup-protoc to v3

[alessio-perugini]

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• [x] The PR has no duplicates (please search among the Pull Requests before creating one)
• [x] The PR follows our contributing guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)
• [ ] UPGRADING.md has been updated with a migration guide (for breaking changes)
• [ ] configuration.schema.json updated if new parameters are added.

What kind of change does this PR introduce?

Bump of setup-protoc action

What is the new behavior?

Does this PR introduce a breaking change, and is titled accordingly?

Other information