Fix a syntax error in the task definition.

tasks/deb-addons.yml

@@ -1,10 +1,10 @@
 ---
-- name:
-  block: Install the packages required by the gitea viewers
-  - name:
-     apt:
-       pkg: '{{ gitea_addons_deb_packages }}'
-       state: present
-       cache_valid_time: 1800
+- name: Install the packages required by the gitea viewers
+  block:
+    - name: Install the packages required by the gitea viewers
+      apt:
+        pkg: '{{ gitea_addons_deb_packages }}'
+        state: present
+        cache_valid_time: 1800
 
   tags: [ 'git', 'gitea', 'gitea_addons' ]