For what it is worth, Asia/Calcutta was already renamed to Asia/Kolkata many years ago. The old name, Asia/Calcutta is preserved as a backwards compatibility alias to Asia/Kolkata.
As I understand it, it's not even close: nowadays
Mumbai aka Bombay has more than 2x the people of Kolkata aka Calcutta.
Also, "Mumbai" is more commonly used in English to refer
to the name of the city. So this suggests that we should
change it to Asia/Mumbai.
Further comments are welcome.