Don't specify the encoding when it's utf-8.

src/websockets/frames.py

@@ -447,7 +447,7 @@ def parse(cls, data: bytes) -> Close:
         """
         if len(data) >= 2:
             (code,) = struct.unpack("!H", data[:2])
-            reason = data[2:].decode("utf-8")
+            reason = data[2:].decode()
             close = cls(code, reason)
             close.check()
             return close

src/websockets/legacy/protocol.py

@@ -1036,7 +1036,7 @@ async def read_message(self) -> Data | None:
 
         # Shortcut for the common case - no fragmentation
         if frame.fin:
-            return frame.data.decode("utf-8") if text else frame.data
+            return frame.data.decode() if text else frame.data
 
         # 5.4. Fragmentation
         fragments: list[Data] = []