Remove unmaintained RPM packaging

See OBS packaging at
https://lab.nexedi.com/nexedi/slapos.package/-/tree/master/obs/re6st

re6stnet.spec

-%define _builddir %(pwd)
-%define ver %(python2 re6st/version.py)
-%define units re6stnet.service re6st-registry.service
-
-Summary:    resilient, scalable, IPv6 network application
-Name:       re6stnet
-Version:    %(set %ver; echo ${1%%-*})
-Release:    %(set %ver; echo ${1#*-})
-License:    GPLv2+
-Group:      Applications/Internet
-BuildArch:  noarch
-Requires:   babeld = 1.12.1-nxd3
-Requires:   iproute
-Requires:   openssl
-Requires:   openvpn >= 2.4
-Requires:   openvpn < 2.5
-Requires:   python >= 2.7
-Requires:   pyOpenSSL >= 0.13
-Requires:   python-setuptools
-%if 0%{?fedora}
-BuildRequires: python3-devel
-%endif
-Recommends: python-miniupnpc
-Conflicts:  re6st-node
-
-%description
-
-%build
-make
-# Fix shebangs before Fedora's shebang mangling
-%if 0%{?fedora}
-pathfix.py -i %{__python3} -p -n $(grep -l -R -e "#\!.*python$")
-%endif
-
-%install
-set $RPM_BUILD_ROOT
-make install PREFIX=%_prefix MANDIR=%_mandir DESTDIR=$1 %{?_unitdir:UNITDIR=%{_unitdir}}
-# Exclude man pages because they will be compressed.
-find $1 -mindepth 1 -path \*%_mandir -prune -o \
-  -name re6st\* -prune -printf /%%P\\n > INSTALLED
-
-%clean
-rm -rf "$RPM_BUILD_ROOT" INSTALLED
-
-%files -f INSTALLED
-%_mandir/*/*
-
-%post
-if [ $1 -eq 1 ]; then
-    /bin/systemctl preset %{units} || :
-fi >/dev/null 2>&1
-
-%preun
-if [ $1 -eq 0 ]; then
-    /bin/systemctl --no-reload disable %{units} || :
-    /bin/systemctl stop %{units} || :
-fi >/dev/null 2>&1
-
-%postun
-/bin/systemctl daemon-reload >/dev/null 2>&1 || :
-if [ $1 -ge 1 ]; then
-    /bin/systemctl try-restart %{units} >/dev/null 2>&1 || :
-fi