Updated rust edition

It has been quite a while
;)

Cargo.lock

@@ -1,6 +1,6 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "anstream"

Cargo.toml

@@ -2,7 +2,7 @@
 name = "huffman"
 version = "0.1.0"
 authors = ["Michalis Marcoux"]
-edition = "2021"
+edition = "2024"
 
 [dependencies]
 bit-vec = "0.8"