spec: Install osbuild-depsolve-dnf not dnf5

On Fedora 40 we switched to dnf5 too early. There is going to be a new
version in Fedora 41 soon, with breaking API changes, so in order to
reduce the number of things we need to support, switch back to using
libdnf on Fedora 40 (and 41 until dnf5 version 5.2.0 is available,
see #1769)

osbuild.spec

@@ -137,12 +137,7 @@ manifests and osbuild.
 Summary:        Dependency solving support for DNF
 Requires:       %{name} = %{version}-%{release}
 
-# Fedora 40 and later use libdnf5, RHEL and Fedora < 40 use libdnf
-%if 0%{?fedora} >= 40
-Requires: python3-libdnf5 >= 5.1.1
-%else
 Requires: python3-libdnf
-%endif
 
 %description    depsolve-dnf
 Contains depsolving capabilities for package managers.
@@ -213,12 +208,7 @@ install -p -m 0755 data/10-osbuild-inhibitor.rules %{buildroot}%{_udevrulesdir}
 
 # Install `osbuild-depsolve-dnf` into libexec
 mkdir -p %{buildroot}%{_libexecdir}
-# Fedora 40 and later use dnf5-json, RHEL and Fedora < 40 use dnf-json
-%if 0%{?fedora} >= 40
-install -p -m 0755 tools/osbuild-depsolve-dnf5 %{buildroot}%{_libexecdir}/osbuild-depsolve-dnf
-%else
 install -p -m 0755 tools/osbuild-depsolve-dnf %{buildroot}%{_libexecdir}/osbuild-depsolve-dnf
-%endif
 
 %check
 exit 0