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>

dumpet.spec

@@ -30,9 +30,6 @@ rm -rf %{buildroot}
 mkdir -p %{buildroot}/%{_bindir}
 make DESTDIR=%{buildroot} install
 
-%clean
-rm -rf %{buildroot}
-
 %files
 %defattr(-,root,root,-)
 %doc README TODO COPYING