various minor spelling tweaks (#9783)

doc/datasets/kddcup99.rst

doc/datasets/labeled_faces.rst

doc/modules/calibration.rst

doc/modules/gaussian_process.rst

doc/modules/manifold.rst

doc/modules/multiclass.rst

doc/modules/neighbors.rst

doc/modules/neural_networks_unsupervised.rst

doc/modules/pipeline.rst

doc/modules/preprocessing.rst

doc/modules/scaling_strategies.rst

doc/modules/svm.rst

doc/themes/scikit-learn/static/ML_MAPS_README.rst

doc/tutorial/statistical_inference/unsupervised_learning.rst

doc/tutorial/text_analytics/working_with_text_data.rst