[test] Remove `describeVariants` helper #27962

Job	Run time
deploy-target	12s
publish-turbopack-npm-packages	0s
build	2m 46s
build-wasm (web)	20s
stable - x86_64-unknown-linux-gnu - node@16	51s
build-wasm (nodejs)	3m 7s
Upload Turbopack Bytesize metrics to Datadog	0s
Deploy examples	0s
Deploy preview tarball	2m 22s
Potentially publish release	0s
Release Stats	0s
	9m 38s

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