tests: add a new `import_x_json2.v` skipped valgrind test

vlib/v/tests/valgrind/import_x_json2.v

@@ -0,0 +1,6 @@
+import x.json2
+
+fn main() {
+	x := '[[],[],[]]'
+	println(json2.raw_decode(x) ?)
+}

vlib/v/tests/valgrind/valgrind_test.v

@@ -29,6 +29,7 @@ const skip_valgrind_files = [
 	'vlib/v/tests/valgrind/fn_with_return_should_free_local_vars.v',
 	'vlib/v/tests/valgrind/option_simple.v',
 	'vlib/v/tests/valgrind/string_plus_string_plus.v',
+	'vlib/v/tests/valgrind/import_x_json2.v',
 ]
 
 fn vprintln(s string) {