Truncated sources tab don't render short attribution

[sophiamersmann]

Description

Tabs in the sources modal are truncated with '...' if they're too long. If they're truncated, then the short attribution is not rendered.

Expected behaviour

The short attribution should be rendered. The '...' should be rendered after the short attribution.

Steps to reproduce

1. Go to https://ourworldindata.org/grapher/agri-environmental-policies-gdp
2. Open the sources modal
3. Note that one of the tabs has a lot of white space

Screenshots

Technical explanation

overflow: ellipsis is applied the the button element but apparently can't deal with nested spans

Additional context

We want to move away from truncation and render multi-line labels instead, see #3654. If we do that, then fixing this is obsolete.