build(#2772): declare enumflags2 at the workspace level

`cargo add -p hive-jobq` wrote the version into the crate's own manifest
instead of `[workspace.dependencies]`, which is how every other shared
dep here is declared and the thing that stops two members drifting onto
different versions of the same crate.

Cargo.toml

@@ -51,6 +51,7 @@ chrono = { version = "0.4", default-features = false, features = [
 ] }
 clap = { version = "4", features = ["derive"] }
 clap_complete = "4"
+enumflags2 = { version = "0.7.12", features = ["serde"] }
 indicatif = "0.18"
 hive-sh4re = { path = "hive-sh4re" }
 hive-agent-sock = { path = "hive-agent-sock" }