Use official MariaDB builds for Ubuntu bionic

We had been using the Ubuntu 17.10 "artful" builds for Ubuntu 18.04
"bionic" but there are now official bionic builds.

README.md

@@ -25,7 +25,6 @@ If setting up Tor relays, you need to install the [ansible-relayor](https://gith
 
 ## Todo
 
-- Update packages for Ubuntu 18.04 (mariadb currently using packages for 17.10 artful)
 - Switch from `cron-apt` to [`unattended-upgrades`](https://wiki.debian.org/UnattendedUpgrades)
 
 ## License

roles/mariadb/templates/mariadb.list.j2

@@ -1,12 +1,7 @@
 # {{ ansible_managed }}
 {% if ansible_distribution == 'Ubuntu' %}
 
-{% if ansible_distribution_version is version_compare('18.04', '==') %}
-# 2018-03-17: no Ubuntu 18.04 "bionic" packages yet, so use 17.10 "artful"
-deb [arch=amd64,i386] http://mariadb.mirror.serveriai.lt/repo/10.2/ubuntu artful main
-{% else %}
 deb [arch=amd64,i386] http://mariadb.mirror.serveriai.lt/repo/10.2/ubuntu {{ ansible_distribution_release }} main
-{% endif %}
 
 {% elif ansible_distribution == 'Debian' %}