correlatorFlowCharmHadrons: Fix missing using directives

Author: vkucera

PWGHF/HFC/TableProducer/correlatorFlowCharmHadrons.cxx

@@ -45,6 +45,8 @@
 #include <vector>
 
 using namespace o2;
+using namespace o2::framework;
+using namespace o2::framework::expressions;
 using namespace o2::hf_centrality;
 using namespace o2::hf_evsel;