bpo-41123: Remove PyUnicode_AsUnicodeCopy in 3.10 (GH-21227)

(cherry picked from commit 2ea6a9928e4fa135888cc8f4733c28d93e642301)

Co-authored-by: Inada Naoki <songofacandy@gmail.com>
diff --git a/Doc/c-api/unicode.rst b/Doc/c-api/unicode.rst
index 2bf4a0f..b261efe 100644
--- a/Doc/c-api/unicode.rst
+++ b/Doc/c-api/unicode.rst
@@ -700,6 +700,8 @@
    :c:func:`PyUnicode_AsWideChar`, :c:func:`PyUnicode_ReadChar` or similar new
    APIs.
 
+   .. deprecated-removed:: 3.3 3.10
+
 
 .. c:function:: PyObject* PyUnicode_TransformDecimalToASCII(Py_UNICODE *s, Py_ssize_t size)