chore(cargo): Update `unicode-linebreak`

[Hywan]

unicode-linebreak 0.1.5 has been released. It removes the build.rs script (it's moved in another separate internal crate). Moving to 0.1.5 removes the following dependencies from the tree:

• ahash,
• aho-corasick,
• hashbrown,
• once_cell,
• regex,
• regex-syntax,
• version_check,
• wasi.

This isn't negligible.

Also, ahash was at version 0.7.6 (latest version is —at the time of writing— 0.8.8), which doesn't compile on Rust nightly. ahash was required by hashbrown, which was required as a build-dependency of unicode-linebreak 0.1.4. It's no longer the case in 0.1.5.