C++: fix bug in serialization code (doesn't request correct version for CurrentTimeElement)

cpp/src/monoformat_structured.cpp

@@ -1899,7 +1899,11 @@ ElementType CurrentTimeElement::elementType() const {
 }
 
 std::uint32_t CurrentTimeElement::minimumFormatVersion() const {
-    return 1;
+    if (static_cast<std::uint8_t>(m_textFlags) != 0) {
+        return 2;
+    } else {
+        return 1;
+    }
 }
 
 std::size_t CurrentTimeElement::serializeTo(std::span<std::byte> target, std::uint32_t formatVersion) const {