message: doc(README): Use ubuntu keyserver for apt-key
  As pgp.mit.edu has become extremely unreliable, this switches to
  keyserver.ubuntu.com for retrieval of package keys
  Change-Type: patch
diff: @@ -50,7 +50,7 @@ installers for all supported operating systems.
  2. Trust Bintray.com's GPG key:
  ```sh
  - sudo apt-key adv --keyserver hkp://pgp.mit.edu:80 --recv-keys 379CE192D401AB61
  + sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 379CE192D401AB61
  ```
  3. Update and install:
  