Fix `clippy::legacy_numeric_constants` lint on nightly

[baumanj]

See https://rust-lang.github.io/rust-clippy/master/index.html#/legacy_numeric_constants

Hopefully this fixes https://github.com/mozilla/mp4parse-rust/actions/runs/8598206617/job/23558557224 I couldn't reproduce it locally, but the fix didn't seem to break either stable or nightly locally either, so I figure if this passes CI, it should fix the issue.

[kinetiknz]

Thanks Jon!