Text field with multiple values does not take size into account

Problem/Motivation

In #3151119: Text field with multiple values overflows on narrow screens → a width:100% was added for text fields inside tables in the seven theme. This makes that text fields always take the full width of the tabel (in multiple elements).
This however ignores the size attribute of those elements.

Steps to reproduce

Create multiple text field.
On edit form see it takes full width.
Change size in form display settings.
Note that the text field is always full width.

Disabling the width:100% line (in dev tools) does take the size attribute correctly into account, but that then would reintroduce the other problem.