Legend kwarg scatteroffsets vs. scatteryoffsets

In current HEAD of `v1.2.x` the docstring of `Axes.legend` and `Figure.legend` is not compatible with the kwargs accepted by `legend.Legend` (and also found in `legend_handler`).

axes/figure docstring: `scatteroffsets`
legend/legend_handler docstring/code: `scatteryoffsets`

I would have fixed it and opened a pull request but I am not sure which one is intended.