Remove unnecessary GPG keys setting for YUM repos.

We add the GPG keys in the previous task so there is no need to
do this inside the YUM task, also, it breaks things because Ansible
expects this to be a string and it's getting a list.

Change-Id: I82f1095bd0e21d76d0246b0c22792878edfb44bf

tasks/ceph_preinstall_yum.yml

@@ -80,7 +80,6 @@
     gpgcheck: yes
     enabled: yes
     priority: 50
-    gpgkey: "{{ ceph_gpg_keys }}"
     state: present
 
 - name: Add ceph noarch repo
@@ -92,5 +91,4 @@
     gpgcheck: yes
     enabled: yes
     priority: 50
-    gpgkey: "{{ ceph_gpg_keys }}"
     state: present