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>

pesign-test-app.spec

@@ -56,9 +56,6 @@ pesign -l -i %{buildroot}/%{_datadir}/%{name}-%{version}/%{name}-signed.efi | gr
 pesign -l -i %{buildroot}/%{_datadir}/%{name}-%{version}/%{name}-signed.efi | grep -c -q '^The signer.s common name is Fedora Secure Boot Signer$'
 %endif
 
-%clean
-rm -rf %{buildroot}
-
 %files
 %defattr(-,root,root,-)
 %doc README COPYING