Import OptimzeResult from scipy.optimize to remove DeprecationWarning (…

…#1764)

Summary:
Getting rid of

> /botorch/botorch/generation/gen.py:34: DeprecationWarning: Please use `OptimizeResult` from the `scipy.optimize` namespace, the `scipy.optimize.optimize` namespace is deprecated.
>   from scipy.optimize.optimize import OptimizeResult

Pull Request resolved: #1764

Reviewed By: esantorella

Differential Revision: D44405681

Pulled By: Balandat

fbshipit-source-id: 727d47e6b2522f73a6b55c5e2b99f4932d209218

botorch/generation/gen.py

@@ -31,7 +31,7 @@
 from botorch.optim.stopping import ExpMAStoppingCriterion
 from botorch.optim.utils import _filter_kwargs, columnwise_clamp, fix_features
 from botorch.optim.utils.timeout import minimize_with_timeout
-from scipy.optimize.optimize import OptimizeResult
+from scipy.optimize import OptimizeResult
 from torch import Tensor
 from torch.optim import Optimizer