Apply suggestion from @srittau

Co-authored-by: Sebastian Rittau <sebastian.rittau@zfutura.de>

Author: donbarbos

stdlib/_thread.pyi

@@ -88,7 +88,7 @@ def exit() -> NoReturn: ...
 @deprecated("Obsolete synonym. Use `exit()` instead.")
 def exit_thread() -> NoReturn: ...  # undocumented
 def allocate_lock() -> LockType: ...
-@deprecated("Obsolete synonym. Use `allocate()` instead.")
+@deprecated("Obsolete synonym. Use `allocate_lock()` instead.")
 def allocate() -> LockType: ...  # undocumented
 def get_ident() -> int: ...
 def stack_size(size: int = 0, /) -> int: ...