DOC add spaces before colons in docstrings (#7589)

sklearn/base.py

sklearn/covariance/graph_lasso_.py

sklearn/datasets/mldata.py

sklearn/datasets/olivetti_faces.py

sklearn/datasets/samples_generator.py

sklearn/datasets/species_distributions.py

sklearn/datasets/svmlight_format.py

sklearn/datasets/twenty_newsgroups.py

sklearn/decomposition/dict_learning.py

sklearn/feature_extraction/dict_vectorizer.py

sklearn/feature_extraction/text.py

sklearn/gaussian_process/gpc.py

sklearn/gaussian_process/gpr.py

sklearn/linear_model/ransac.py

sklearn/manifold/locally_linear.py

sklearn/metrics/classification.py

sklearn/metrics/cluster/supervised.py

sklearn/metrics/pairwise.py

sklearn/mixture/dpgmm.py

sklearn/mixture/gaussian_mixture.py