Remove the gray container around the main page div

Dependencies

• [2] SIIXRVUE Tweak CSS for img/logo.
• [3] ELABMHJI * hydra: layout changes
• [4] ZI535LI6 * hydra: 'new' UI for project/jobset/job/build
• [5] J5UVLXOK * Start of a basic Catalyst web interface.
• [6] FKK2ZSTL * Split the CSS.
• [7] TEZTE7QT bigger min-height, max-width for page
• [8] QL55ECJ6 - adapted ui for hydra, more in line with nixos.org website

Change contents

• replacement in src/root/static/css/hydra.css at line 8
  [3.169]→[2.0:14](∅→∅)
  − height: 6em;
  [3.169]

  [3.8897]
  + height: 6em;
• edit in src/root/static/css/nixos-site.css at line 2
  [3.3727]→[3.3727:3770](∅→∅)
  − background-color: gray;

  − margin: 0;
• edit in src/root/static/css/nixos-site.css at line 10
  [3.3934]→[3.3934:4034](∅→∅)
  −

  − /* Put a rounded border around the page. */

  − border: 1px solid black;

  − padding: 1em;