[flang] Remove runtime check from OpenFile::Close()

[klausler]

Summary

In error cases it is possible to CLOSE a unit that has not
been successfully connected, so don't crash when the file descriptor
is negative.

flang/runtime/file.cpp

void OpenFile::Predefine(int fd) {
   nextId_ = 0;
   pending_.reset();
   mayRead_ = fd == 0;
   mayWrite_ = fd != 0;
   mayPosition_ = false;
 }
 
 void OpenFile::Close(CloseStatus status, IoErrorHandler &handler) {
-  CheckOpen(handler);
   pending_.reset();
   knownSize_.reset();
   switch (status) {
   case CloseStatus::Keep:
     break;
   case CloseStatus::Delete:
     if (path_.get()) {
       ::unlink(path_.get());