Configure merge queue for rustfmt

[Kobzol]

Should be merged in cooperation with rust-lang/rustfmt#6989.

[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/rustfmt':
      Rulesets:
          Updating 'main'
            Required status checks: (i686-pc-windows-gnu, nightly) (integration_id: 15368), (i686-pc-windows-gnu, stable) (integration_id: 15368), (i686-pc-windows-msvc, nightly) (integration_id: 15368), (i686-pc-windows-msvc, stable) (integration_id: 15368), (x86_64-apple-darwin, nightly) (integration_id: 15368), (x86_64-apple-darwin, stable) (integration_id: 15368), (x86_64-pc-windows-gnu, nightly) (integration_id: 15368), (x86_64-pc-windows-gnu, stable) (integration_id: 15368), (x86_64-pc-windows-msvc, nightly) (integration_id: 15368), (x86_64-pc-windows-msvc, stable) (integration_id: 15368), (x86_64-unknown-linux-gnu, nightly) (integration_id: 15368), (x86_64-unknown-linux-gnu, stable) (integration_id: 15368), rustdoc check (integration_id: 15368) => rustdoc check (integration_id: 15368), test conclusion (integration_id: 15368)
            Merge queue grouping strategy: Allgreen
            Merge queue max entries to build: 5
            Merge queue max entries to merge: 5
            Merge queue merge_method: Merge
            Merge queue min entries to merge: 1
            Merge queue timeout: 60
            Merge queue wait time for min group size: 5
            Require merge queue: true