token: Update to v5 for solana-program 2.0 compatibility (#6907)
Updating to allow for version <= 2.0 of the solana crates can appear as
a breaking change for new projects, since cargo pulls in the latest
version of all dependencies, and once there's an attempt to mix v1 and
v2, downstream users will see errors.
This is made worse that the patch versions will quietly pick up the v2
dependency, so if someone doesn't know how to manipulate a cargo
lockfile, they will get build errors and won't know how to resolve them.
All other SPL crates contain a new breaking version (new major for
crates on v1 or more, new minor for crates on v0.X), except for
spl-token.
Bump spl-token to v5.
Jon C