refactor: migrate variant api (#6238)

utils/edit.cc

@@ -214,7 +214,7 @@ static bool replaceURL(tr_variant* metainfo, std::string_view oldval, std::strin
                     auto const newstr = replaceSubstr(sv, oldval, newval);
                     fmt::print("\tReplaced in 'announce-list' tier #{:d}: '{:s}' --> '{:s}'\n", tierCount + 1, sv, newstr);
                     node->clear();
-                    tr_variantInitStr(node, newstr);
+                    *node = newstr;
                     changed = true;
                 }