Fix mismatched punctuation in Debug impl of AttrId

[dtolnay]

I noticed this odd line in ast-tree output.

$ echo '#[attr] struct S;' | rustc -Zunpretty=ast-tree -

...
            attrs: [
                Attribute {
                    kind: Normal(
                        NormalAttr {
                            item: AttrItem {
                                path: Path {
                                    segments: [
                                        PathSegment {
                                            ident: attr#0,
                                            args: None,
                                        },
                                    ],
                                    tokens: None,
                                },
                                args: Empty,
                            },
                        },
                    ),
                    id: AttrId(0)],      // <------
                    style: Outer,
                },

[rustbot]

r? @petrochenkov

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[compiler-errors]

thanks! looks like it was a mistake from #105880, but that seems like the only one that got messed up.

r? @compiler-errors @bors r+ rollup

[bors]

📌 Commit c5da061 has been approved by compiler-errors

It is now in the queue for this repository.