cpp linter fix

Author: Shirajum Monira

PWGCF/FemtoUniverse/Tasks/femtoUniversePairTaskTrackV0Extended.cxx

@@ -35,6 +35,7 @@
 #include <memory>
 #include <string>
 #include <vector>
+#include <set>
 
 using namespace o2;
 using namespace o2::soa;