remove mentions of --prebuilt-platform #2261

Job	Run time
check-changes	19s
check-changes	19s
ran-none	0s
ran-none	0s
start-macos-x86-64-tests / test-rust-macos-x86-64	32m 38s
start-macos-x86-64-tests / test-rust-macos-x86-64	32m 38s
start-nix-linux-aarch64-build-default-test / nix-linux-arm64	35m 59s
start-nix-linux-aarch64-build-default-test / nix-linux-arm64	35m 59s
start-nix-linux-aarch64-cargo-build-test / nix-linux-arm64	42m 48s
start-nix-linux-aarch64-cargo-build-test / nix-linux-arm64	42m 48s
start-nix-linux-x86-64-tests / nix-linux-x86	39m 17s
start-nix-linux-x86-64-tests / nix-linux-x86	39m 17s
start-nix-macos-apple-silicon-tests / nix-apple-silicon	30m 45s
start-nix-macos-apple-silicon-tests / nix-apple-silicon	37m 42s
start-roc-benchmarks / benchmark roc programs	8m 14s
start-roc-benchmarks / benchmark roc programs	8m 14s
start-ubuntu-x86-64-nix-tests-debug / cargo test debug nix	18m 13s
start-ubuntu-x86-64-nix-tests-debug / cargo test debug nix	18m 13s
start-ubuntu-x86-64-tests / test zig, rust, wasm...	30m 18s
start-ubuntu-x86-64-tests / test zig, rust, wasm...	30m 18s
start-windows-release-build-test / windows-release-build	12m 19s
start-windows-release-build-test / windows-release-build	12m 19s
start-windows-tests / windows-test-subset	32m 8s
start-windows-tests / windows-test-subset	32m 8s
ran-full	0s
ran-full	1s
finish	1s
finish	1s
	9h 32m 56s

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