update crashkernel-howto
    
    Resolves: bz2073676
    Upstream: Fedora
    Conflict: None
    
    commit 683ff878213ea2a58971902f90f9dd77d4e64b8f
    Author: Coiby Xu <coxu@redhat.com>
    Date:   Mon Apr 18 15:54:53 2022 +0800
    
        update crashkernel-howto
    
        1. clean up left crashkernel.default
        2. fix a few typos and grammar mistakes
        3. ask the users to refer to `man kdumpctl` for reset-crashkernel
    
        Philipp Rudo <prudo@redhat.com>
    
        Signed-off-by: Coiby Xu <coxu@redhat.com>
    
    Signed-off-by: Coiby Xu <coxu@redhat.com>