token: Bump to v6 for Solana v2 compatibility (#6918)

program/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "spl-token"
-version = "5.0.0"
+version = "6.0.0"
 description = "Solana Program Library Token"
 authors = ["Solana Labs Maintainers <maintainers@solanalabs.com>"]
 repository = "https://github.com/solana-labs/solana-program-library"