Refactored the file path handling in the main script.

- Replaced `os.path` module with `pathlib` for the file path handling to improve code readability and simplicity.

yt_dlp/__main__.py

@@ -4,14 +4,15 @@
 # $ python3 -m yt_dlp
 
 import sys
+from pathlib import Path
+
+import yt_dlp
 
 if __package__ is None and not getattr(sys, 'frozen', False):
     # direct call of __main__.py
-    import os.path
-    path = os.path.realpath(os.path.abspath(__file__))
-    sys.path.insert(0, os.path.dirname(os.path.dirname(path)))
-
-import yt_dlp
+    path = Path(__file__).resolve()
+    sys.path.insert(0, str(path.parent.parent))
 
 if __name__ == '__main__':
+
     yt_dlp.main()