There is no problem with the absolute maximum ratings.
However, there might be problems with the other parameters of this optocoupler. The MIDI specification calls for a high-speed optocoupler. which the PC123 is not.
At the 5 mA specified for the MIDI current loop, the PC123 has a guaranteed current transfer ratio of at least 50 %. This means that to get a 5 V signal out, you need at load resistor (Rd above) of at least 5V/2.5mA = 2 kΩ. As the datasheet shows, the typical raise/fall times in this case are about 20 µs:
This is way more than the 2 µs limit of the specification. At 31250 baud, the length of a single bit is 32 µs; this optocoupler will distort the signal beyond all recognition.
With the Arduino's Schmitt trigger inputs, and a portion of luck, you might actually be able to get the signal out, so you might as well try it. However, this is nothing I would recommend you rely on.
If you don't want to buy a suitable optocoupler like the 6N137, 6N138, or H11L1, you could try to use additional circuitry to prevent the phototransistor from saturating and to amplify its signal:
