Use consistent re-export from ruff_source_file (#9320)

Right now, we both re-export (via `pub use`) and mark the modules
themselves a `pub`, so they can be imported through two different paths.

crates/ruff_python_ast/src/whitespace.rs

@@ -1,5 +1,5 @@
 use ruff_python_trivia::{indentation_at_offset, is_python_whitespace, PythonWhitespace};
-use ruff_source_file::{newlines::UniversalNewlineIterator, Locator};
+use ruff_source_file::{Locator, UniversalNewlineIterator};
 use ruff_text_size::{Ranged, TextRange, TextSize};
 
 use crate::Stmt;