Fix comment to mention that Transient tasks are used for root tasks #8644

Job	Run time
build-wasm (web)	3m 38s
build-wasm (nodejs)	3m 41s
build	2m 25s
deploy-target	11s
stable - x86_64-apple-darwin - node@16	4m 21s
stable - aarch64-apple-darwin - node@16	4m 2s
stable - x86_64-pc-windows-msvc - node@16	9m 23s
stable - x86_64-unknown-linux-gnu - node@16	3m 37s
stable - aarch64-unknown-linux-gnu - node@16	3m 34s
Deploy examples	0s
Deploy preview tarball	2m 2s
Potentially publish release	0s
Upload Turbopack Bytesize metrics to Datadog	0s
Release Stats	0s
	36m 54s

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