rpminspect: add duplicate dependency to appease rpmispect

[skip changelog]

systemd.spec

@@ -510,6 +510,10 @@ a userspace out-of-memory (OOM) killer.
 %package tests
 Summary:       Internal unit tests for systemd
 Requires:      %{name}%{_isa} = %{version}-%{release}
+# This dependency is provided transitively. Also add it explicitly to
+# appease rpminspect, https://github.com/rpminspect/rpminspect/issues/1231:
+Requires:      %{name}-libs%{_isa} = %{version}-%{release}
+
 License:       LGPL-2.1-or-later
 
 %description tests