xds: revert a workaround made in #4413 (#4428)

Author: easwars

xds/internal/test/xds_integration_test.go

@@ -83,11 +83,6 @@ func TestMain(m *testing.M) {
 	// spawns the management server and is blocked on the call to `Serve()`.
 	leakcheck.RegisterIgnoreGoroutine("e2e.StartManagementServer")
 
-	// Remove this once https://github.com/envoyproxy/go-control-plane/pull/430
-	// is merged. For more information about this goroutine leak, see:
-	// https://github.com/envoyproxy/go-control-plane/issues/429.
-	leakcheck.RegisterIgnoreGoroutine("(*server).StreamHandler")
-
 	cancel, err := setupManagementServer()
 	if err != nil {
 		log.Printf("setupManagementServer() failed: %v", err)