[jsinterp] Escape regex that looks like nested set

Closes #5749

yt_dlp/jsinterp.py

@@ -343,7 +343,8 @@ class JSInterpreter:
             inner, outer = self._separate(expr, expr[0], 1)
             if expr[0] == '/':
                 flags, outer = self._regex_flags(outer)
-                inner = re.compile(inner[1:], flags=flags)
+                # Avoid https://github.com/python/cpython/issues/74534
+                inner = re.compile(inner[1:].replace('[[', r'[\['), flags=flags)
             else:
                 inner = json.loads(js_to_json(f'{inner}{expr[0]}', strict=True))
             if not outer: