refactor: Rename fs::path::u8string() to fs::path::utf8string()

doc/developer-notes.md

@@ -1406,7 +1406,7 @@ A few guidelines for introducing and reviewing new RPC interfaces:
 
   - *Rationale*: User-facing consistency.
 
-- Use `fs::path::u8string()` and `fs::u8path()` functions when converting path
+- Use `fs::path::u8string()`/`fs::path::utf8string()` and `fs::u8path()` functions when converting path
   to JSON strings, not `fs::PathToString` and `fs::PathFromString`
 
   - *Rationale*: JSON strings are Unicode strings, not byte strings, and