warning message when following installation instructions

Steps to Reproduce:

1. Follow the instructions for Linux installation https://www.edgedb.com/install#linux-debianubuntults
2. Step configures the package repo:
`
echo deb [signed-by=/usr/local/share/keyrings/edgedb-keyring.gpg]\
https://packages.edgedb.com/apt \
$(grep "VERSION_CODENAME=" /etc/os-release | cut -d= -f2) main \
| sudo tee /etc/apt/sources.list.d/edgedb.list
`
3. sudo apt-get update

This command will show a non-fatal warning stating that the 'release does not support architecture i386'

The message is, as noted, non-fatal but I had to research it to find that out. This could create confusion or friction in the install or lead the user to think that it has failed.

The warning can be silenced by adding a minus arch flag to the options:

`
deb [signed-by=/usr/local/share/keyrings/edgedb-keyring.gpg arch-=i386 ] \
https://packages.edgedb.com/apt \
main
`

Start with the Linux installation instructions at https://www.edgedb.com/install#linux-debianubuntults and locate the command that adds the APT repository. Update the repository options as described in the issue, then run the installation instructions and confirm that sudo apt-get update no longer reports the i386 architecture warning.

Written by the indexing model from the issue text.