Remove once_cell dependency (#31493)

removing once_cell dep imported from #31439

it should work just fine

Release Notes:

- N/A

crates/assistant_tools/src/edit_agent/create_file_parser.rs

@@ -1,10 +1,10 @@
-use once_cell::sync::Lazy;
 use regex::Regex;
 use smallvec::SmallVec;
+use std::cell::LazyCell;
 use util::debug_panic;
 
-const START_MARKER: Lazy<Regex> = Lazy::new(|| Regex::new(r"\n?```\S*\n").unwrap());
-const END_MARKER: Lazy<Regex> = Lazy::new(|| Regex::new(r"\n```\s*$").unwrap());
+const START_MARKER: LazyCell<Regex> = LazyCell::new(|| Regex::new(r"\n?```\S*\n").unwrap());
+const END_MARKER: LazyCell<Regex> = LazyCell::new(|| Regex::new(r"\n```\s*$").unwrap());
 
 #[derive(Debug)]
 pub enum CreateFileParserEvent {