No. This is the quality of the file produced by the Google api. There is no option to download a higher bitrate mp3 file.
I think what matters is how it sounds. It always sounds very good to me. Bear in mind that this is a computer generated voice, not chamber music. 32 Kbps for 24 Hz in mono should be more than good enough quality for a human voice and a computer generated one probably needs even less because the audio is very clean and simple. If anyone were to decide that it did not sound good enough for them, I would expect that to be due to the voice synthesis, and not the quality of the mp3 encoding.
Since these voices have to be downloaded from the cloud, I assume that Google made a balanced choice that would yield the best sound without wasting bandwidth.