Add missing AdderGate class or remove references

[mtreinish]

What should we add?

The 1.3.0 release notes referred to an AdderGate class, described as: "AdderGate implements standard addition including a carry-out" and this is also referred to in several docstrings for specific adder classes. But I have found no class definition for AdderGate. Either we should add the missing class or remove the references (I removed the release note for 1.3.0 in #13447 already)

[alexanderivrii]

There was an AdderGate class during the initial implementation, but it was later renamed to HalfAdderGate. Maybe we have indeed missed a few places.

[ShellyGarion]

closed by #13502