Update requirement file syntax

tasks/install-requirements.yml

@@ -2,14 +2,6 @@
 
 name: Installation des dépendances pour HedgeDoc
   apt:
-    name: "{{ packages }}"
+    name: ['postgresql','nodejs','git','npm','yarn','bash','nginx']
     state: present
     update_cache: yes
-  vars:
-    packages:
-      - postgresql
-      - nodejs
-      - git
-      - npm
-      - yarn
-      - bash