Change module pip with multiple packages to remove deprecated syntax

tasks/alerta.yml

@@ -13,12 +13,13 @@
 
 - name: "Ensure PIP packages"
   pip:
-    name: '{{ item }}'
+    name: '{{ packages }}'
     state: 'present'
-  with_items:
-    - 'alerta-server'
-    - 'alerta'
-    - 'uwsgi'
+  vars:
+    packages:
+      - 'alerta-server'
+      - 'alerta'
+      - 'uwsgi'
 
 - name: "Remove directories for web UI"
   file: