Going off google the energy required to heat the oceans by 1 degree is approximately 5.4*10^21 kj, or 1389 trillion GWh, or the energy output of over 170 million nuclear power plants over an entire year. Safe to say putting all the server farms in the world in there still isn’t going to make a dent.

It might affect local temperature by a relevant amount if there’s too many in one spot perhaps, and that could be pretty bad. But generally, saving energy is a good thing.