Fix `ImpersonateTarget` sanitization (#13791)

Fix 32809eb2da

Authored by: bashonly

yt_dlp/YoutubeDL.py

@@ -3716,6 +3716,8 @@ class YoutubeDL:
                 return {k: filter_fn(v) for k, v in obj.items() if not reject(k, v)}
             elif isinstance(obj, (list, tuple, set, LazyList)):
                 return list(map(filter_fn, obj))
+            elif isinstance(obj, ImpersonateTarget):
+                return str(obj)
             elif obj is None or isinstance(obj, (str, int, float, bool)):
                 return obj
             else: