fix: replace vulnerable users crate with whoami

The users crate (RUSTSEC-2025-0040) has an unfixable vulnerability.
Replace it with the maintained whoami crate for getting the current
username. Also remove metrics.yml workflow as it provided no value.

Cargo.toml

@@ -21,7 +21,7 @@ zeroize = "1.7"
 log = "0.4"
 env_logger = { version = "0.11", default-features = false, features = ["color", "humantime"] }
 chrono = { version = "0.4", default-features = false, features = ["clock", "std"] }
-users = "0.11"
+whoami = "1.0"
 zbus = { version = "3.15", default-features = false, features = ["tokio"] }
 mpris = "2.0"
 upower_dbus = "0.3"