v.gen.c: fix fn variadic of reference param (#11115)

cmd/tools/vtest-cleancode.v

@@ -34,6 +34,7 @@ const (
 		'vlib/builtin/int.v' /* TODO byteptr: vfmt converts `pub fn (nn byteptr) str() string {` to `nn &byte` and that conflicts with `nn byte` */,
 		'vlib/builtin/string_charptr_byteptr_helpers.v' /* TODO byteptr: a temporary shim to ease the byteptr=>&byte transition */,
 		'vlib/v/tests/interop_test.v', /* bad comment formatting */
+		'vlib/v/tests/vargs_reference_param_test.v', /* variadic reference params */
 		'vlib/v/gen/js/tests/js.v', /* local `hello` fn, gets replaced with module `hello` aliased as `hl` */
 	]
 	vfmt_verify_list                = [