util-mariadb: use python3-mysqldb on Bullseye

roles/float-util-mariadb/tasks/monitoring.yml

 # TODO(godog) setup ai-metrics-exporter scraping
 
-- name: Install exporter and deps
+- name: Install exporter
   apt:
     name: "{{ packages }}"
     state: present
   vars:
     packages:
       - prometheus-mysqld-exporter
-      - python-mysqldb
+
+- name: Install Ansible Mysql deps
+  apt:
+    name: "{{ 'python-mysqldb' if float_debian_dist == 'buster' else 'python3-mysqldb' }}"
+    state: present
 
 - include_tasks: user.yml
   vars: