Remove Python 3.8 support (#11321)

Closes #10086
Authored by: bashonly

yt_dlp/__init__.py

@@ -1,8 +1,8 @@
 import sys
 
-if sys.version_info < (3, 8):
+if sys.version_info < (3, 9):
     raise ImportError(
-        f'You are using an unsupported version of Python. Only Python versions 3.8 and above are supported by yt-dlp')  # noqa: F541
+        f'You are using an unsupported version of Python. Only Python versions 3.9 and above are supported by yt-dlp')  # noqa: F541
 
 __license__ = 'The Unlicense'