Remove %clean section

None of currently supported distributions need that.
Last one was EL5 which is EOL for a while.

Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>

openvswitch.spec

@@ -415,9 +415,6 @@ rm -f $RPM_BUILD_ROOT/%{_bindir}/ovs-benchmark \
     fi
 %endif
 
-%clean
-rm -rf $RPM_BUILD_ROOT
-
 %preun
 %if 0%{?systemd_preun:1}
     %systemd_preun %{name}.service