Add proptest regression (#8396)

# Description

I found this when I was checking out my commits. It must have happened
during one of the random test failures that I've been getting quite
often recently.

# User-Facing Changes

None?

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-command/proptest-regressions/format_conversions/nuon.txt

@@ -21,3 +21,4 @@ cc d4afccc51ed9d421bdb7e1723e273dfb6e77c3a449489671a496db234e87c5ed # shrinks to
 cc 515a56d73eb1b69290ef4c714b629421989879aebd57991bd2c2bf11294353b1 # shrinks to s = "\\\\𐊀{"
 cc 111566990fffa432acd2dbc845141b0e7870f97125c7621e3ddf142204568246 # shrinks to s = "'\":`"
 cc 0424c33000d9188be96b3049046eb052770b2158bf5ebb0c98656d7145e8aca9 # shrinks to s = "0"
+cc 39026f9657675bde623b9710c6fa113dee418142d0c25733b0798102948d0213 # shrinks to s = "}𐀋⋆"