MAINT ensure that examples figures are displayed in the correct order

doc/datasets/index.rst

doc/modules/biclustering.rst

doc/modules/clustering.rst

doc/modules/computational_performance.rst

doc/modules/covariance.rst

doc/modules/cross_decomposition.rst

doc/modules/decomposition.rst

doc/modules/density.rst

doc/modules/ensemble.rst

doc/modules/feature_extraction.rst

doc/modules/feature_selection.rst

doc/modules/gaussian_process.rst

doc/modules/isotonic.rst

doc/modules/kernel_approximation.rst

doc/modules/label_propagation.rst

doc/modules/lda_qda.rst

doc/modules/learning_curve.rst

doc/modules/linear_model.rst

doc/modules/manifold.rst

doc/modules/mixture.rst