refactor: remove unnecessary empty check in ReplaceAll

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Co-authored-by: nunoplopes <2998477+nunoplopes@users.noreply.github.com>

Author: Copilot

cpp2rust/converter/converter_lib.cpp

@@ -764,8 +764,6 @@ void Unwrap(std::string &s, std::string_view prefix, std::string_view suffix) {
 
 std::string ReplaceAll(std::string str, std::string_view from,
                        std::string_view to) {
-  if (from.empty())
-    return str;
   size_t pos = 0;
   while ((pos = str.find(from, pos)) != std::string::npos) {
     str.replace(pos, from.size(), to);