refmt removes unremovable parentheses

[smorimoto]

We use these helpers in our tests, but refmt breaks them.
https://github.com/ocsigen/tyxml/blob/8551b673857fdc1defebe7c502ffcb920f04009e/test/tyxml_test.ml#L81-L85

Actual behavior:

1. !:(<p />)
2. !:<p />

Expected behaviour:

1. !:(<p />)
2. !:(<p />)