Compensating voltage drop in circuit
Things like relays and solenoid valves tend to be quite tolerant of deviations in their actual applied voltages and currents and the specified values.

So, without knowing a whole lot of detail -- the valve will be a bit slower and wimpier at 23V, but probably not that bad.  Whether that makes a difference to you depends on whether you're designing your system so that the valve is riding on the hairy edge of failure (which is not a robust way to design a system), or whether you're designing your system with plenty of margin.