Zoom incompatible with "grace" option

When using the [grace option](https://www.chartjs.org/docs/latest/axes/cartesian/linear.html#linear-axis-specific-options) (options.scales[scaleId].grace) on the y axis, zooming and dezooming will not keep the correct aspect ratio of the y-scale and make the curve look flatter and flatter.
Here’s a simple jsfiddle example: https://jsfiddle.net/n9j5gho1/