You can file for divorce if your spouse has undergone conversion to another religion and has ceased to be a Hindu.
File a Case
It is very important to note that since your spouse has converted to another religion it does not automatically end your marriage to them. You must still file for divorce.
Even if your spouse has converted to another religion the divorce proceedings will happen under the Hindu law and not the religion your spouse converted to. This is because your marriage to your spouse happened under Hindu law.