build: lock execa to >=2.0.0

[xmlking]

Before submitting this PR:

Proposing to upgrade execa version to >=2.0.0 to mitigate this vulnerability discovered via docker scout quickview nhost/hasura-auth:0.28.0 scan.

https://scout.docker.com/vulnerabilities/id/GMS-2020-2?s=gitlab&n=execa&t=npm&vr=%3C2.0.0

Checklist

• [x] No breaking changes
• [x] Tests pass
• [ ] New features have new tests
• [ ] Documentation is updated

Breaking changes

Avoid breaking changes and regressions. If you feel it is unavoidable, make it explicit in your PR comment so we can review it and see how to handle it.

Tests

• please make sure your changes pass the current tests (Use the make test or the make watch command).
• if you are introducing a new feature, please write as much tests as possible.

Documentation

Please make sure the documentation is updated accordingly, in particular:

• Workflows. Workflows are Mermaid sequence diagrams
• Schema. The schema in a Mermaid ER diagram
• Environment variables. Please adjust the .env.example file accordingly
• OpenApi specifications. We are using inline JSDoc annotations

[dbarrosop]

I don't know why github "emptied" the commit when I rebased it... Anyway, opened #500 with your commit