bpo-36346: Add Py_DEPRECATED to deprecated unicode APIs (GH-20878)

Co-authored-by: Kyle Stanley <aeros167@gmail.com>
Co-authored-by: Victor Stinner <vstinner@python.org>
(cherry picked from commit 2c4928d37edc5e4aeec3c0b79fa3460b1ec9b60d)
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index e0457ae..5302641 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -1668,6 +1668,10 @@
 
 static volatile int x;
 
+/* Ignore use of deprecated APIs */
+_Py_COMP_DIAG_PUSH
+_Py_COMP_DIAG_IGNORE_DEPR_DECLS
+
 /* Test the u and u# codes for PyArg_ParseTuple. May leak memory in case
    of an error.
 */
@@ -1844,6 +1848,7 @@
 
     Py_RETURN_NONE;
 }
+_Py_COMP_DIAG_POP
 
 static PyObject *
 unicode_aswidechar(PyObject *self, PyObject *args)
@@ -2064,6 +2069,10 @@
     return PyUnicode_TransformDecimalToASCII(unicode, length);
 }
 
+/* Ignore use of deprecated APIs */
+_Py_COMP_DIAG_PUSH
+_Py_COMP_DIAG_IGNORE_DEPR_DECLS
+
 static PyObject *
 unicode_legacy_string(PyObject *self, PyObject *args)
 {
@@ -2086,6 +2095,7 @@
 
     return u;
 }
+_Py_COMP_DIAG_POP
 
 static PyObject *
 getargs_w_star(PyObject *self, PyObject *args)