[DOC] axis name cropped

[glemaitre]

In some figure, the axis name is cropped. We should probably used tight_layout explicitly:

https://imbalanced-learn.org/stable/auto_examples/over-sampling/plot_shrinkage_effect.html#sphx-glr-auto-examples-over-sampling-plot-shrinkage-effect-py

[seanbenhur]

Hi @glemaitre, I have fixed this issue and submitted a PR can you look onto it!?