Fix comment to mention that Transient tasks are used for root tasks #8646

Job	Run time
build-wasm (web)	24s
deploy-target	8s
build	2m 36s
build-wasm (nodejs)	25s
stable - x86_64-apple-darwin - node@16	1m 19s
stable - aarch64-apple-darwin - node@16	1m 7s
stable - x86_64-pc-windows-msvc - node@16	2m 54s
stable - x86_64-unknown-linux-gnu - node@16	1m 29s
stable - aarch64-unknown-linux-gnu - node@16	1m 50s
Deploy examples	0s
Upload Turbopack Bytesize metrics to Datadog	0s
Potentially publish release	0s
Deploy preview tarball	0s
Release Stats	0s
	12m 12s

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