Cargo.toml: set resolver = 2

cole-h · zhaofengli · commit fdb9d06ff63a · 2023-12-18T09:28:43.000-07:00
There are some 2021-edition crates that Cargo was warning about.
diff --git a/Cargo.toml b/Cargo.toml
@@ -1,4 +1,5 @@
 [workspace]
+resolver = "2"
 
 members = [
 	"attic",
