Does the story of the Parsi merchant Ratanji in Chapter 14 mention Gajanan Maharaj?

No, the provided text about the merchant Ratanji from Chapter 14 makes no reference to Gajanan Maharaj. The narrative is centered entirely on Sai Baba of Shirdi. It was Das Ganu who advised the childless Ratanji to 'Go to Shirdi' and take the darshan of Sai Baba. The text describes Ratanji's meeting with Sai Baba in the Masjid. While the honorific 'Maharaj' is used in the chapter, as in 'Seeing Maharaj, the heap of merit, love surged within him,' it is being used as a term of respect for Sai Baba himself, not as a reference to a different saint like Gajanan Maharaj. The entire account details Ratanji's plea to Sai Baba.