ansible-inventories/bitegra#31 Update to latest versions

defaults/main.yml

-alerta_version_api: 8.1.0
-alerta_version_web_ui: 8.0.1
+# From https://hub.docker.com/r/alerta/alerta-web
+alerta_version_api: 8.3.1
+
+# From https://github.com/alerta/alerta-webui
+alerta_version_web_ui: 8.3.2