ansible/playbooks/general#117 Update apt repository setting

tasks/main.yml

@@ -25,7 +25,7 @@
 
     - name: Apt Repository
       apt_repository:
-        repo: 'deb http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/4.0 multiverse'
+        repo: 'deb [signed-by=/etc/apt/trusted.gpg.d/mongodb.gpg] http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/4.0 multiverse'
         state: present
         mode: 0644