Fix wrong Qt version variable

Author: 5yutan5

qdarktheme/qtpy/qt_version.py

@@ -5,14 +5,18 @@
 
 __version__: str | None = None
 if QT_API == "PySide6":
-    from PySide6 import __version__  # type: ignore
+    from PySide6.QtCore import qVersion  # type: ignore
+
+    __version__ = qVersion().decode("utf-8")
 elif QT_API == "PyQt6":
-    from PyQt6.QtCore import PYQT_VERSION_STR  # type: ignore
+    from PyQt6.QtCore import qVersion  # type: ignore
 
-    __version__ = PYQT_VERSION_STR
+    __version__ = qVersion()
 elif QT_API == "PyQt5":
-    from PyQt5.QtCore import PYQT_VERSION_STR  # type: ignore
+    from PyQt5.QtCore import qVersion  # type: ignore
 
-    __version__ = PYQT_VERSION_STR
+    __version__ = qVersion()
 elif QT_API == "PySide2":
-    from PySide2 import __version__  # type: ignore  # noqa: F401
+    from PySide2.QtCore import qVersion  # type: ignore
+
+    __version__ = qVersion().decode("utf-8")