crates-build-env repo, remove required approvals

[syphar]

so maintainers could just merge things if it fits.

[syphar]

r? @marcoieni

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[github-actions]

Dry-run check results

[WARN  rust_team::sync] sync-team is running in dry mode, no changes will be applied.
[INFO  rust_team::sync] synchronizing crates-io
[INFO  rust_team::sync] synchronizing github
[INFO  rust_team::sync] 💻 Repo Diffs:
    📝 Editing repo 'rust-lang/crates-build-env':
      Rulesets:
          Updating 'master'
            Required approvals: 1 => 0