Switch from yum to dnf to install packages

Use of ansible.builtin.yum is no longer supported on Python 3, so it
triggers linter errors there that prevent the gate from working.
Switching to ansible.builtin.dnf should fix that.

Change-Id: I46e491efe3e31e7f92f6e4436f8aea1e97fa3be5

tasks/client.yaml

@@ -26,7 +26,7 @@
   when: ansible_os_family | lower == 'redhat'
 
 - name: Ensure unzip is avaliable to unzip ISO file
-  ansible.builtin.yum:
+  ansible.builtin.dnf:
     name: unzip
     state: present
 
@@ -56,7 +56,7 @@
     key: "{{ thales_client_working_dir }}/pubkey.asc"
 
 - name: Install Security World RPMs
-  ansible.builtin.yum:
+  ansible.builtin.dnf:
     name: "{{ packages }}"
   vars:
     packages: