Update the gpg key of the repo.aptly.info repository in the README

[maciej-gol]

Fixes

Using the gpg key in the README:

Err:1 http://repo.aptly.info squeeze InRelease                                                         
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EE727D4449467F0E

Requirements

All new code should be covered with tests, documentation should be updated. CI should pass.

Description of the Change

The actual repo uses different gpg key. Either the repo has been taken over, or the README is out of date.

Checklist

• unit-test added (if change is algorithm)
• functional test added/updated (if change is functional)
• man page updated (if applicable)
• bash completion updated (if applicable)
• documentation updated
• author name in AUTHORS