.txt decks reportedly don't get saved when they're loaded. (#5459)

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/deck/deck_loader.cpp

@@ -139,6 +139,7 @@ bool DeckLoader::updateLastLoadedTimestamp(const QString &fileName, FileFormat f
     // Perform file modifications
     switch (fmt) {
         case PlainTextFormat:
+            result = saveToFile_Plain(&file);
             break;
         case CockatriceFormat:
             setLastLoadedTimestamp(QDateTime::currentDateTime().toString());