Update eframe requirement from 0.26 to 0.28

Updates the requirements on [eframe](https://github.com/emilk/egui) to permit the latest version.
- [Release notes](https://github.com/emilk/egui/releases)
- [Changelog](https://github.com/emilk/egui/blob/master/CHANGELOG.md)
- [Commits](emilk/egui@0.26.0...0.28.1)

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

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

crates/spectator/Cargo.toml

@@ -20,7 +20,7 @@ argmin = { version = "0.10.0", path = "../argmin", default-features = false, fea
 bytes = "1.4.0"
 clap = { version = "4.1.7", features = ["derive"] }
 dashmap = { version = "6.0", features = ["serde"], optional = true }
-eframe = { version = "0.26", features = ["ron", "persistence"], optional = true }
+eframe = { version = "0.28", features = ["ron", "persistence"], optional = true }
 egui_dock = { version = "0.11", optional = true }
 egui_extras = { version = "0.26", optional = true }
 egui_plot = { version = "0.26", optional = true }