message: Fix 2 ClangTidyReadability findings:
  * redundant string conversion
  #codehealth
  Tested:
  Local presubmit tests passed.
diff: @@ -247,7 +247,7 @@ void GenericTableEditorDialog::Import() {
  return;
  }
  - InputFileStream ifs(filename.toStdString().c_str());
  + InputFileStream ifs(filename.toStdString());
  if (!LoadFromStream(&ifs)) {
  QMessageBox::warning(this, windowTitle(), tr("Import failed"));
  return;
  @@ -267,7 +267,7 @@ void GenericTableEditorDialog::Export() {
  return;
  }
  - OutputFileStream ofs(filename.toStdString().c_str());
  + OutputFileStream ofs(filename.toStdString());
  if (!ofs) {
  QMessageBox::warning(this, windowTitle(), tr("Export failed"));
  return;
  