build: bump rustfmt edition to 2024

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: hseeberger

rustfmt.toml

@@ -1,4 +1,4 @@
-edition = "2021"
+edition = "2024"
 
 max_width       = 100
 reorder_imports = true