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>

libsvm.spec

@@ -240,9 +240,6 @@ if [ -x %{_bindir}/gtk-update-icon-cache ]; then
 fi
 
 
-%clean
-rm -rf %{buildroot}
-
 
 %files
 %defattr(-,root,root,-)