Move dependencies to workspace (#4495)

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Inspired by:

44d65f41ac/Cargo.toml (L65)

I took the liberty of removing that comment since I *think* that I got
all "relevant" ones (showing up more than once, sort of).

crates/epaint/Cargo.toml

@@ -84,7 +84,7 @@ nohash-hasher.workspace = true
 parking_lot.workspace = true   # Using parking_lot over std::sync::Mutex gives 50% speedups in some real-world scenarios.
 
 #! ### Optional dependencies
-bytemuck = { version = "1.7.2", optional = true, features = ["derive"] }
+bytemuck = { workspace = true, optional = true, features = ["derive"] }
 
 ## Enable this when generating docs.
 document-features = { workspace = true, optional = true }
@@ -94,7 +94,7 @@ puffin = { workspace = true, optional = true }
 rayon = { version = "1.7", optional = true }
 
 ## Allow serialization using [`serde`](https://docs.rs/serde) .
-serde = { version = "1", optional = true, features = ["derive", "rc"] }
+serde = { workspace = true, optional = true, features = ["derive", "rc"] }
 
 # native:
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]