[ie/youtube] Remove broken `n` function extraction fallback (#10396)

Closes #10391
Authored by: pukkandan, seproDev

Co-authored-by: pukkandan <pukkandan.ytdlp@gmail.com>

yt_dlp/extractor/youtube.py

@@ -3151,17 +3151,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
 
         func_name = self._extract_n_function_name(jscode)
 
-        # For redundancy
-        func_code = self._search_regex(
-            rf'''(?xs){func_name}\s*=\s*function\s*\((?P<var>[\w$]+)\)\s*
-                     # NB: The end of the regex is intentionally kept strict
-                     {{(?P<code>.+?}}\s*return\ [\w$]+.join\(""\))}};''',
-            jscode, 'nsig function', group=('var', 'code'), default=None)
-        if func_code:
-            func_code = ([func_code[0]], func_code[1])
-        else:
-            self.write_debug('Extracting nsig function with jsinterp')
-            func_code = jsi.extract_function_code(func_name)
+        func_code = jsi.extract_function_code(func_name)
 
         self.cache.store('youtube-nsig', player_id, func_code)
         return jsi, player_id, func_code