Tweak CSS for img/logo.

Dependencies

• [2] ELABMHJI * hydra: layout changes
• [3] ZI535LI6 * hydra: 'new' UI for project/jobset/job/build
• [4] FKK2ZSTL * Split the CSS.
• [5] QL55ECJ6 - adapted ui for hydra, more in line with nixos.org website
• [6] J5UVLXOK * Start of a basic Catalyst web interface.

Change contents

• replacement in src/root/static/css/hydra.css at line 8
  [3.169]→[2.962:975](∅→∅)
  − width: 8em;
  [3.169]

  [3.8897]
  + height: 6em;