Fix some mistakes in lastly added roles

amavis/tasks/main.yml

@@ -1,6 +1,4 @@
 - name: ensure packages are installed
   apt:
-    name: '{{ item }}'
+    name: amavis
     state: present
-  with_items:
-  - amavis

spamassassin/README.md

@@ -1,4 +1,4 @@
-# Courier
+# Spamassassin
 
 Installation and basic configuration of spamassassin
 

spamassassin/tasks/main.yml

@@ -1,6 +1,4 @@
 - name: ensure packages are installed
   apt:
-    name: '{{ item }}'
+    name: spamassassin
     state: present
-  with_items:
-  - spamassassin