Fix protobuf deserialization of `ValidatorEntityType` #3289

Job	Run time
get-branch-name	1s
build-cedar-drt / Build and test DRT (stable)	8m 59s
build-cedar-java / Build on Linux	13m 1s
build-tiny-todo / Build and test TinyTodo (stable)	5m 12s
build-cedar-java / Build on macOS	12m 59s
build-cedar-examples-hello-world / Build and test Rust example (stable)	1m 43s
build-wasm / Build and test Wasm example (stable)	6m 21s
run-cedar-examples-use-cases / Run example use cases (stable)	1m 20s
run-integration-tests / Run integration tests (stable)	5m 12s
	54m 48s

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