Please don't use short key id

[Nobuto Murata]

[config.yaml]
  "install_keys":
    "default": |
      - '7AD95B3F'
    "type": "string"
    "description": "YAML list of GPG keys for installation sources, as a string. For\
      \ apt repository\nURLs, use the public key ID used to verify package signatures.\
      \ For \nother sources such as PPA, use empty string. This list must have the\
      \ \nsame number of elements as install_sources, even if the key items are \n\
      all empty string. An example to go with the above for install_sources:\n install_keys:\
      \ |\n - \"\"\n - \"\"\n"