Fix printing of the preamble in generated Rust code. #2541

Job	Run time
Rustfmt	9s
Check	1m 58s
Build wit-bindgen (x86_64-linux, ubuntu-latest)	1m 42s
Test (ubuntu-latest, c)	4m 26s
Build wit-bindgen (x86_64-macos, macos-latest, x86_64-apple-darwin)	1m 45s
Crate Unit Tests	57s
Test (ubuntu-latest, rust)	4m 37s
verify-publish	1m 49s
Build wit-bindgen (aarch64-macos, macos-latest, aarch64-apple-darwin)	1m 14s
Test (ubuntu-latest, teavm-java)	5m 3s
Build wit-bindgen (x86_64-windows, windows-latest)	4m 8s
Test (ubuntu-latest, go)	5m 48s
Build wit-bindgen (aarch64-linux, ubuntu-latest, aarch64-unknown-linux-gnu)	1m 58s
Test (ubuntu-latest, csharp)	7m 55s
Test (macos-latest, c)	4m 25s
Test (macos-latest, rust)	4m 10s
Test (macos-latest, teavm-java)	4m 3s
Test (macos-latest, go)	9m 53s
Test (macos-latest, csharp)	6m 13s
Test (windows-latest, c)	8m 28s
Test (windows-latest, rust)	9m 15s
Test (windows-latest, teavm-java)	9m 29s
Test (windows-latest, go)	10m 34s
Test (windows-latest, csharp)	31m 11s
Record the result of testing and building steps	1s
	2h 21m 11s

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