ci: unpin the wasi-nn tasks from an older Ubuntu (#6089)

* ci: unpin the wasi-nn tasks from an older Ubuntu

Previously, OpenVINO's lack of APT packages for Ubuntu 22.04 (`jammy`)
prevented us from upgrading the GitHub runner to use `ubuntu-latest`. I
updated the `install-openvino-action` to substitute in the `focal`
packages in this case (this is what the OpenVINO team considers the fix)
so this pin should no longer be necessary. Fixes #5408.

(Run all CI actions: prtest:full)

* vet: audit the openvino version bump

crates/wasi-nn/Cargo.toml

@@ -17,7 +17,7 @@ anyhow = { workspace = true }
 wiggle = { workspace = true }
 
 # These dependencies are necessary for the wasi-nn implementation:
-openvino = { version = "0.4.2", features = ["runtime-linking"] }
+openvino = { version = "0.5.0", features = ["runtime-linking"] }
 thiserror = { workspace = true }
 
 [build-dependencies]