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>

salt.spec

@@ -333,9 +333,6 @@ mkdir %{_tmppath}/salt-test-cache
 PYTHONPATH=%{pythonpath} %{__python} setup.py test --runtests-opts=-u
 %endif
 
-%clean
-rm -rf %{buildroot}
-
 %files
 %defattr(-,root,root,-)
 %doc $RPM_BUILD_DIR/%{name}-%{version}/%{name}-%{version}/LICENSE