rpm: switch to ansible-core on RHEL 8

RHEL 8.6+ ships ansible-core. This version is much newer and
better-supported than the old ansible package in the
ansible-2.9-for-rhel-8-x86_64-rpms repository.

Update the el8 packaging to depend on ansible-core instead of ansible.

(cherry picked from commit 76220f2)

cephadm-ansible.spec.in

@@ -11,15 +11,10 @@ Source0:        %{name}-%{version}-%{shortcommit}.tar.gz
 
 BuildArch:      noarch
 
-%if 0%{?el8}
-BuildRequires: ansible >= 2.9
-Requires: ansible >= 2.9
-%else
 BuildRequires: ansible-core >= 2.9
 BuildRequires: ansible-collection-community-general
 Requires: ansible-core >= 2.9
 Requires: ansible-collection-community-general
-%endif
 
 %description
 cephadm-ansible is a collection of Ansible playbooks to simplify workflows that are not covered by cephadm.