Remove duplicate signal declaration in DownloadThread

Eliminated a redundant declaration of the 'update_details' signal in the DownloadThread class to clean up the code and prevent confusion.

src/core/ytsage_downloader.py

@@ -34,7 +34,6 @@ class DownloadThread(QThread):
     error_signal = Signal(str)
     file_exists_signal = Signal(str)  # New signal for file existence
     update_details = Signal(str)  # New signal for filename, speed, ETA
-    update_details = Signal(str)  # New signal for filename, speed, ETA
 
     def __init__(
         self,