Cleanup + fix for regression since UI refinement branch

[nckrtl]

• Removed invalid width calculation. I assumed it fixed the aligningment of the dt element, but as @parallels999 mentioned here https://github.com/barryvdh/laravel-debugbar/pull/1601#discussion_r1550017214 its invalid CSS and doesn't do anything. The alignment must've been fixed by something else.

• Brought back the padding of the search bar container in the messages tab to prevent overlap on the scrollbar. See https://github.com/barryvdh/laravel-debugbar/pull/1601#discussion_r1550033594

• Merged duplicate selector dl.phpdebugbar-widgets-kvlist dt

[erikn69]

Almost, but i can handle it now 👍

[nckrtl]

Hmm, that would trigger my OCD still :) more than happy to reduce the width more. Seems it would need another trim of 10px on either side.