[cleanup] Misc (#11216)

- Add Python 3.13 to CI, finalize 3.13 support
- Remove Python 3.8 from CI in preparation for removing 3.8 support
- Document that PyPy3.8 and PyPy3.9 are no longer supported
- Usual documentation fixes and code cleanup

Closes #8248, Closes #11146, Closes #11149, Closes #11211
Authored by: Grub4K, grqz, DTrombett, KarboniteKream, bashonly, mikkovedru, seproDev

Co-authored-by: N/Ame <173015200+grqz@users.noreply.github.com>
Co-authored-by: DTrombett <d@trombett.org>
Co-authored-by: =?UTF-8?q?Klemen=20Ko=C5=A1ir?= <klemen.kosir@kream.io>
Co-authored-by: bashonly <88596187+bashonly@users.noreply.github.com>
Co-authored-by: Mikko Vedru <mikko.vedru@gmail.com>
Co-authored-by: sepro <sepro@sepr0.com>

yt_dlp/extractor/veoh.py

@@ -8,7 +8,8 @@ from ..utils import (
     int_or_none,
     parse_duration,
     qualities,
-    try_get,
+    remove_start,
+    strip_or_none,
 )
 
 
@@ -108,7 +109,7 @@ class VeohIE(InfoExtractor):
 
         categories = metadata.get('categoryPath')
         if not categories:
-            category = try_get(video, lambda x: x['category'].strip().removeprefix('category_'))
+            category = remove_start(strip_or_none(video.get('category')), 'category_')
             categories = [category] if category else None
         tags = video.get('tags')