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>

perl-DateTime-Calendar-Mayan.spec

@@ -37,9 +37,6 @@ find %{buildroot} -depth -type d -exec rmdir {} ';' 2>/dev/null
 %check
 make test
 
-%clean
-rm -rf %{buildroot} 
-
 %files
 %defattr(-,root,root,-)
 %doc README Changes LICENSE Todo