Review proportions when two fields are next to each other

[GuillaumeRx]

Verify that the form component doesn't try to take more than 50% of space when put in a row

To reproduce:

  <Form name="form">
      <Box direction="horizontal">
        <Field label="foo">
          <Selector title="bar" name="test">
            <SelectorOption value="one">
              <Card title="test" value="test" />
            </SelectorOption>
          </Selector>
        </Field>
        <Field label="baz">
          <Input name="baz" placeholder="Enter something..." />
        </Field>
      </Box>
    </Form>