Remove an unused dependency (#10747)

## Summary

Continuation of #10475, I improved [`cargo
shear`](https://github.com/Boshen/cargo-shear) even more.

We can put this in CI once I test it a bit more, given that [ignoring
false
positives](https://github.com/Boshen/cargo-shear?tab=readme-ov-file#ignore-false-positives)
has been implemented.

## Test Plan

`cargo check --all-features --all-targets`

crates/ruff_python_parser/Cargo.toml

@@ -18,7 +18,6 @@ ruff_python_ast = { path = "../ruff_python_ast" }
 ruff_text_size = { path = "../ruff_text_size" }
 
 anyhow = { workspace = true }
-bitflags = { workspace = true }
 bstr = { workspace = true }
 is-macro = { workspace = true }
 itertools = { workspace = true }