Fix cart sidebar style

[orzechdev]

I want to merge this change because... it fixes hiding item in the cart sidebar and items quantity message.

Previously it was sometimes hidden by prices amount (when the cart list was scrolled to the very end):

Now:

Screenshots

Pull Request Checklist

1. All visible strings are translated with proper context.
2. All data-formatting is locale-aware (dates, numbers, and so on).
3. The changes are tested.
4. The code is documented (docstrings, project documentation).
5. Changes are mentioned in the changelog.

Test Environment Config

API_URI=https://master.staging.saleor.rocks/graphql/

[patrys]

Task linked: SALEOR-670 One item in the basket is treated as a items

[krzysztofwolski]

Checked against the demo instance and it solves the problem. LGTM!