Describe the bug
CodeSandbox here: https://codesandbox.io/s/quirky-fire-cpj3v7?file=/demo.js

When the DataGrid accepts a gridStyle prop, updates to that prop don't cause the data grid to re-render.

In the above example, if you use the data grid controls to change the density, you'll see the grid re-render in response. However, if you click the button at the top "Reset to Compact", which explicitly sets the grid style to compact, it doesn't re-render (even though you can see the console logging the new grid style):

Impact and severity
This isn't currently a big issue, but it was found as part of elastic/kibana#188495 (comment). We will have a workaround for that PR, but it would be nice if this could be fixed so the workaround can be removed.