add comment for features.BootstrapTokens

Author: carlory

test/e2e/feature/feature.go

@@ -28,7 +28,10 @@ var (
 	// TODO: document the feature (owning SIG, when to use this feature for a test)
 	APIServerIdentity = framework.WithFeature(framework.ValidFeatures.Add("APIServerIdentity"))
 
-	// TODO: document the feature (owning SIG, when to use this feature for a test)
+	// Owner: sig-lifecycle
+	// This label is used for tests which need the following controllers to be enabled:
+	// - bootstrap-signer-controller
+	// - token-cleaner-controller
 	BootstrapTokens = framework.WithFeature(framework.ValidFeatures.Add("BootstrapTokens"))
 
 	// TODO: document the feature (owning SIG, when to use this feature for a test)