[BBB 3.0] Repo is unsigned / public key not available

[Ithanil]

When trying to install version jammy-300 via bbb-install, the installation fails due to unsigned repository / unavailable public key:

Err:17 https://ubuntu.bigbluebutton.org/jammy-300 bigbluebutton-jammy InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 37B5DD5EFAB46452
Reading package lists...
W: GPG error: https://ubuntu.bigbluebutton.org/jammy-300 bigbluebutton-jammy InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 37B5DD5EFAB46452
E: The repository 'https://ubuntu.bigbluebutton.org/jammy-300 bigbluebutton-jammy InRelease' is not signed.
+ apt-get -y -o Dpkg::Options::=--force-confdef -o Dpkg::Options::=--force-confnew dist-upgrade

Executing gpg --keyserver [keyserver.ubuntu.com](http://keyserver.ubuntu.com/) --recv-keys 37B5DD5EFAB46452 beforehand doesn't help.

[Ithanil]

Fixed with #744