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>

pentaho-reporting-flow-engine.spec

@@ -49,9 +49,6 @@ cp -p build/lib/flow-engine.jar $RPM_BUILD_ROOT%{_javadir}/flow-engine.jar
 mkdir -p $RPM_BUILD_ROOT%{_javadocdir}/%{name}
 cp -rp build/api $RPM_BUILD_ROOT%{_javadocdir}/%{name}
 
-%clean
-rm -rf $RPM_BUILD_ROOT
-
 %files
 %defattr(0644,root,root,0755)
 %doc licence-LGPL.txt README.txt ChangeLog.txt