Fix small styling issues on workspace page

Created by: eseliger

• Fixes a stray border right of the diff stat when no timer is shown
• Aligns the diff stats properly
• Fixes the icons shrinking on smaller screens

Closes https://github.com/sourcegraph/sourcegraph/issues/36613

Test plan

Verified manually the expected changes did happen.

App preview:

• Web
• Storybook

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