Those are not needed since F28 and since this package is built only for
F28+, remove those scriptlets entirely.
Also fixes:
/sbin/ldconfig: relative path `1' used to build cache
warning: %postun(libijs-0.35-2.gitd26d2bb.fc28.x86_64) scriptlet failed, exit status 1
Non-fatal POSTUN scriptlet failure in rpm package libijs
Non-fatal POSTUN scriptlet failure in rpm package libijs
Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>