This brings us another theoretical problem: someone could spend our
OP_TRUE with a low-fee non-RBF tx, and we'd not be able to use it to
CPFP the tx.  It'd be hard to do, but possible.  I think the network
benefits from using OP_TRUE (anyone can clean, and size, vs some
only-known-to-me pubkey) outweighs the risk, but it'd be nice if OP_TRUE
P2WSH spends were always considered RBF.