Re-format trybuild tests

[jplatte]

Automated with

for file in axum-macros/tests/**/*.rs; do
    rustfmt --edition 2021 "$file"
done

[yanns]

Are the issues on nightly new?

[jplatte]

Ah, that's almost certainly from the changes in this PR. Let me check..

[jplatte]

Yeah, looks like it was just a couple of changed error locations in the trybuild output.