switch from PyQt6 to PySide6

PySide6 uses LGPL instead of GPL, which is much nicer to work with.

logFileModel.py

@@ -1,9 +1,7 @@
 import math
 import re
 from typing import List, Optional
-
-from PyQt6.QtCore import pyqtSignal
-
+from PySide6.QtCore import Signal
 from highlight_regex import HighlightRegex
 from highlighting import Highlighting
 from line import Line
@@ -14,7 +12,7 @@ from settings import Settings
 class LogFileModel:
     _query_highlight: Optional[HighlightRegex] = None
 
-    file_size_changed = pyqtSignal(str)
+    file_size_changed = Signal()
     """Fires when the file size changed. **Note:** uses strings, 
        because int in Qt signal are limited to 32bit."""