regex: use a vector in RegexComponentSetMatcher

Change-Id: Iec466b477144a7332d2f1992691601c738dfc3df
Refs: #4120
diff --git a/src/util/regex/regex-component-set-matcher.hpp b/src/util/regex/regex-component-set-matcher.hpp
index 3c9fae9..5cb9d1f 100644
--- a/src/util/regex/regex-component-set-matcher.hpp
+++ b/src/util/regex/regex-component-set-matcher.hpp
@@ -26,7 +26,7 @@
 
 #include "regex-matcher.hpp"
 
-#include <set>
+#include <vector>
 
 namespace ndn {
 
@@ -63,7 +63,7 @@
   extractComponent(size_t index) const;
 
 private:
-  std::set<shared_ptr<RegexComponentMatcher>> m_components;
+  std::vector<shared_ptr<RegexComponentMatcher>> m_components;
   bool m_isInclusion;
 };