Hardcoded size value for SelectArrayInput

[amilosmanli]

What you were expecting:
SelectArrayInput to honor defaultProps set for MuiSelect component

What happened instead:
SelectArrayInput has a hardcoded size prop that is not possible to override

Steps to reproduce:
add following to the components sections of the theme

MuiSelect: {
      defaultProps: {
        variant: 'outlined',
        size: 'medium',
      },
    },

Related code:
https://github.com/marmelab/react-admin/blob/master/packages/ra-ui-materialui/src/input/SelectArrayInput.tsx#L295

Other information:

Environment

• React-admin version: latest
• Last version that did not exhibit the issue (if applicable):
• React version:
• Browser:
• Stack trace (in case of a JS error):

[antoinefricker]

Thanks for your feedback.
We would gladly welcome a PR from the community for this bugfix!

[slax57]

Fixed in #8562