Core/Dependencies: Update utf8-cpp to version 2.3.4

dep/utf8cpp/utf8/unchecked.h

@@ -179,7 +179,7 @@ namespace utf8
           class iterator : public std::iterator <std::bidirectional_iterator_tag, uint32_t> { 
             octet_iterator it;
             public:
-            iterator () {};
+            iterator () {}
             explicit iterator (const octet_iterator& octet_it): it(octet_it) {}
             // the default "big three" are OK
             octet_iterator base () const { return it; }