roles: strict truthy values

According to Ansible we can use yes, true, True, "or any quoted st-
ring" for a boolean true, but ansible-lint wants us to use either
true or false.

See: https://chronicler.tech/red-hat-ansible-yes-no-and/

roles/php-fpm/tasks/Ubuntu_20.04.yml

@@ -12,7 +12,7 @@
         - php7.4-xml
 
   - name: Install php-fpm and deps
-    ansible.builtin.apt: name={{ php_fpm_packages }} state=present update_cache=yes
+    ansible.builtin.apt: name={{ php_fpm_packages }} state=present update_cache=true
 
   # only copy php-fpm config for vhosts that need WordPress or PHP
   - name: Copy php-fpm pool config