Update syntax of calls to optimize_acqf_mixed_alternating (#2943)

Summary:
Pull Request resolved: #2943

X-link: facebook/Ax#4069

Ax: Update a call to `optimize_acqf_mixed_alternating` to match D79091028 / #2942

BoTorch: Update type annotations to clarify that the argument will not be mutated, allowing Pyre to pass for Ax.

Reviewed By: saitcakmak

Differential Revision: D79107891

fbshipit-source-id: bae5490e8493e7880d78e10b59cb1d89e8e34cfa

Author: esantorella

botorch/optim/optimize_mixed.py

@@ -8,7 +8,8 @@
 import itertools
 import random
 import warnings
-from typing import Any, Callable, Sequence
+from collections.abc import Mapping, Sequence
+from typing import Any, Callable
 
 import torch
 from botorch.acquisition import AcquisitionFunction
@@ -807,8 +808,8 @@ def continuous_step(
 def optimize_acqf_mixed_alternating(
     acq_function: AcquisitionFunction,
     bounds: Tensor,
-    discrete_dims: dict[int, list[float]] | None = None,
-    cat_dims: dict[int, list[float]] | None = None,
+    discrete_dims: Mapping[int, Sequence[float]] | None = None,
+    cat_dims: Mapping[int, Sequence[float]] | None = None,
     options: dict[str, Any] | None = None,
     q: int = 1,
     raw_samples: int = RAW_SAMPLES,