Bump Nix dependency

Dependencies

• [2] 5CNQUQ77 Bump Nix
• [3] 34UH6B6L Build against the bleeding edge of Nix
• [4] OKEMZJLS Bump Nix
• [5] 6K5PBUUN Use buildEnv to combine Hydra's Perl dependencies
• [6] PKTKSVTL Bump Nix
• [7] 4YCF3KBG Concurrent hydra-evaluator
• [8] 7DEMMXE5 Bump Nix
• [*] T4LLYESZ * Nix expression for building Hydra.

Change contents

• replacement in release.nix at line 61
  [3.565]→[2.0:135](∅→∅)
  − rev = "2af5d35fdc1171a9bdab7e2fc005673d76417c06";

  − sha256 = "1q2s4r895qn6sws048j7xwfdpyxm0dwkh52c55535w7x46am33wa";
  [3.565]

  [3.700]
  + rev = "4be4f6de56f4de77f6a376f1a40ed75eb641bb89";

  + sha256 = "0icvbwpca1jh8qkdlayxspdxl5fb0qjjd1kn74x6gs6iy66kndq6";