Fix typo in optimize_homotopy (#2549)

Summary:
Pull Request resolved: #2549

see title

Reviewed By: saitcakmak

Differential Revision: D63236195

fbshipit-source-id: c85b83b8320eb460f9aad89309705cb17e4e2b9b

botorch/optim/optimize_homotopy.py

@@ -78,7 +78,7 @@ def optimize_acqf_homotopy(
         final_options: Options for candidate generation in the last homotopy step.
         batch_initial_conditions: A tensor to specify the initial conditions. Set
             this if you do not want to use default initialization strategy.
-        post_processing_func: Post processing function (such as roundingor clamping)
+        post_processing_func: Post processing function (such as rounding or clamping)
             that is applied before choosing the final candidate.
     """
     candidate_list, acq_value_list = [], []