Remove MultiFidelityAcquisition (facebook#2520)

Summary:

I believe this was originally designed based on the legacy MF models, but it appears to be incompatible with what MBM evolved to be. Here are a few reasons for removing it:
- Some of kwargs that are produced by `MultiFidelityAcquisition.compute_model_dependencies` (e.g., `cost_aware_utility`) are not accepted by the MFKG input constructor.
- The main kwargs that are needed by the MF acquisition functions (`cost_aware_utility`, `project`, `expand`) are readily constructed by the MF input constructors: https://github.com/pytorch/botorch/blob/main/botorch/acquisition/input_constructors.py#L1221
- We strongly discourage subclassing MBM components  and rather encourage expanding the base components to support new use cases. In this case, the MF input constructors seem to have replaced what `MultiFidelityAcquisition` originally aimed to do, while being compatible with the design philosophy.

Discovered while investigating facebook#2514

Differential Revision: D58560934