Remove the kernel from the critpath set
    
    The Linux kernel package is not yet supported by abipkgdiff so
    removing it from the set of packages we are running on, for now.
    
    	* package_list.fedora25-critpath.json: Remove the "kernel" package
    	from the set.
    
    Signed-off-by: Dodji Seketeli <dodji@seketeli.org>