contrib/rpm: fix "--enable-ppp" flag to build without ppp

[thaller@redhat.com: I introduced this bug when taking the original patch].

Fixes: 820f6f3a4a ('contrib/rpm: sync obsoletes_{initscripts_updown,ifcfg_rh} version')

contrib/fedora/rpm/NetworkManager.spec

@@ -878,7 +878,7 @@ autoreconf --install --force
 	--with-pppd="%{_sbindir}/pppd" \
 	--with-pppd-plugin-dir="%{_libdir}/pppd/%{ppp_version}" \
 %else
-	--enable-ppp=yes \
+	--enable-ppp=no \
 %endif
 %if %{with firewalld_zone}
 	--enable-firewalld-zone=yes \