find-provides.ksyms, find-requires.ksyms: avoid awaking debuginfod
    
    Starting with RHEL 9.2 and Fedora 35, debuginfod is enabled by default,
    which leads to significant startup times of various tools
    from the elfutils package (namely, readelf and objdump).
    Unset DEBUGINFOD_URLS to avoid it.
    
    * find-provides.ksyms (DEBUGINFOD_URLS): Unset.
    * find-requires.ksyms (DEBUGINFOD_URLS): Ditto.
    * kernel-srpm-macros.spec (Release): Bump to 18.
    (%changelog): Add a record.
    
    Suggested-by: Panu Matilainen <pmatilai@redhat.com>
    Co-Authored-by: Denys Vlasenko <dvlasenk@redhat.com>
    Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>