Update dashmap requirement from 5.4 to 6.0

Updates the requirements on [dashmap](https://github.com/xacrimon/dashmap) to permit the latest version.
- [Release notes](https://github.com/xacrimon/dashmap/releases)
- [Commits](xacrimon/dashmap@v5.4.0...v6.0.0)

---
updated-dependencies:
- dependency-name: dashmap
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

crates/spectator/Cargo.toml

@@ -19,7 +19,7 @@ anyhow = "1.0"
 argmin = { version = "0.10.0", path = "../argmin", default-features = false, features = ["serde1"] }
 bytes = "1.4.0"
 clap = { version = "4.1.7", features = ["derive"] }
-dashmap = { version = "5.4", features = ["serde"], optional = true }
+dashmap = { version = "6.0", features = ["serde"], optional = true }
 eframe = { version = "0.26", features = ["ron", "persistence"], optional = true }
 egui_dock = { version = "0.11", optional = true }
 egui_extras = { version = "0.26", optional = true }