I had to actually read the FDA page to figure out how this is a problem. Too much Vitamin D for infants with impaired renal (Kidney) function can be bad. It’s unlikely to impact the average infant consuming it.
It takes months of very high consumption of Vitamin D to become toxic. Like 60,000 IU per day (for an adult) for 3+ months continuously.
For comparison baby formula normally contains about 30 IU per 100mL, and they drink about 800ml per day as a newborn (or a total of 180IU per day)
Infant Vitamin D drops are 400IU per drop, these are recommended to give daily in Northern States and Canada in addition to what they get from other sources.