update crashkernel-howto
    
    Resolves: bz1895258
    Upstream: Fedora
    Conflict: None
    
    commit 0e162120b61c9b29a5ecbe7f3e447484b0a27b39
    Author: Coiby Xu <coxu@redhat.com>
    Date:   Mon Dec 13 12:44:14 2021 +0800
    
        update crashkernel-howto
    
        Update crashkernel-howto since crashkernel.default has been removed. The
        documentation is also simplified as a result.
    
        Reviewed-by: Pingfan Liu <piliu@redhat.com>
        Reviewed-by: Philipp Rudo <prudo@redhat.com>
        Signed-off-by: Coiby Xu <coxu@redhat.com>
    
    Signed-off-by: Coiby Xu <coxu@redhat.com>