Bump mlxtend from 0.17.2 to 0.17.3

Bumps mlxtend from 0.17.2 to 0.17.3.

Release notes

Sourced from mlxtend's releases.

Version 0.17.3

New Features

• Add predict_proba kwarg to bootstrap methods, to allow bootstrapping of scoring functions that take in probability values. (#700 via Adam Li)
• Add a cell_values parameter to mlxtend.plotting.heatmap() to optionally suppress cell annotations by setting cell_values=False. (#703

Changes

• Implemented both use_clones and fit_base_estimators (previously refit in EnsembleVoteClassifier) for EnsembleVoteClassifier and StackingClassifier. (#670 via Katrina Ni)
• Switched to using raw strings for regex in mlxtend.text to prevent deprecation warning in Python 3.8 (#688)
• Slice data in sequential forward selection before sending to parallel backend, reducing memory consumption.

Bug Fixes

• Fixes axis DeprecationWarning in matplotlib v3.1.0 and newer. (#673)
• Fixes an issue with using meshgrid in no_information_rate function used by the bootstrap_point632_score function for the .632+ estimate. (#688)
• Fixes an issue in fpmax that could lead to incorrect support values. (#692 via Steve Harenberg)

Commits

• 35f9061 V0.18.0 (#711)
• 081be59 various documentation improvements (#710)
• ab66722 remove redundant line (#708)
• c928fd2 Forward slection reduce mem copy (#705)
• 6dfde8c cell_values option for heatmap (#703)
• df0feb1 [WIP] Adding predict_proba ability to bootstrap_632 functions (#700)
• 727e254 fix eyepad doc (#701)
• 57aa05a Updated appveyor and travis CI for recent software versions (#697)
• 1c39940 Use chain.from_iterable in exhaustive_feature_selector.py (#695)
• 56944fc Fix for bug 690, where fpmax returned incorrect support values (#692)
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