nix/sources.json: update common for the nixpkgs upgrade
For the changelog see:
"common": {
"ref": "master",
"repo": "ssh://git@github.com/dfinity-lab/common",
- "rev": "7278afe2b6ddcd0c78c82fae38160bc4583fc1a6",
+ "rev": "53663c4957c0db10ce9bf8401ed768ad0cb8faa9",
"type": "git"
},
"dfinity": {
