Update Cargo.toml

[nsipplswezey]

Update ps-logger rust code sample to match documentation in Scylla University S210: Using ScyllaDB Drivers Rust and ScyllaDB: Getting Started https://university.scylladb.com/courses/using-scylla-drivers/lessons/rust-and-scylla-2/

The Scylla University Course that references the ps-logger scylla code sample repo specifies different dependencies in the code sample Cargo.toml file that those actually in the repo.

This pull request updates the Cargo.toml file in the scylla code samples repo to match those in Scylla University S210: Using ScyllaDB Drivers Rust and ScyllaDB: Getting Started https://university.scylladb.com/courses/using-scylla-drivers/lessons/rust-and-scylla-2/

[guy9]

Thanks @nsipplswezey