Bump 0.15.4 (#23595)
Just to be sure, I ran the example from #23587 again on this branch:
```console
~/astral/ruff on brent/0.15.4 [$] is 📦 v0.15.4 via 🐍 v3.14.2 via 🦀 v1.93.0
❯ echo 'x = id' | uvx ruff@latest --isolated check - --preview --select ANN003,PLR1712
error: Ruff crashed. If you could open an issue at:
https://github.com/astral-sh/ruff/issues/new?title=%5BPanic%5D
...quoting the executed command, along with the relevant file contents and `pyproject.toml` settings, we'd be very appreciative!
thread 'main' (1681253) panicked at crates/ruff_python_semantic/src/definition.rs:285:26:
index out of bounds: the len is 0 but the index is 0
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
~/astral/ruff on brent/0.15.4 [$] is 📦 v0.15.4 via 🐍 v3.14.2 via 🦀 v1.93.0
❯ echo 'x = id' | just run --isolated check - --preview --select ANN003,PLR1712
cargo run -p ruff -- --isolated check - --preview --select ANN003,PLR1712
Compiling ruff_python_semantic v0.0.0 (/home/brent/astral/ruff/crates/ruff_python_semantic)
Compiling ruff v0.15.4 (/home/brent/astral/ruff/crates/ruff)
Compiling ruff_linter v0.15.4 (/home/brent/astral/ruff/crates/ruff_linter)
Compiling ruff_graph v0.1.0 (/home/brent/astral/ruff/crates/ruff_graph)
Compiling ruff_workspace v0.0.0 (/home/brent/astral/ruff/crates/ruff_workspace)
Compiling ruff_markdown v0.0.0 (/home/brent/astral/ruff/crates/ruff_markdown)
Compiling ruff_server v0.2.2 (/home/brent/astral/ruff/crates/ruff_server)
Finished `dev` profile [unoptimized + debuginfo] target(s) in 23.14s
Running `target/debug/ruff --isolated check - --preview --select ANN003,PLR1712`
warning: Detected debug build without --no-cache.
All checks passed!
```
