bpo-44558: Match countOf `is`/`==` treatment to c (GH-27007)

(cherry picked from commit 6bd3ecfc272b122b55a6adec50dd7a7c868f262f)

Co-authored-by: Rupert Tombs <rupert.tombs@gmail.com>
diff --git a/Modules/_operator.c b/Modules/_operator.c
index d5e092e..f051513 100644
--- a/Modules/_operator.c
+++ b/Modules/_operator.c
@@ -507,12 +507,12 @@ _operator_indexOf_impl(PyObject *module, PyObject *a, PyObject *b)
 /*[clinic input]
 _operator.countOf = _operator.indexOf
 
-Return the number of times b occurs in a.
+Return the number of items in a which are, or which equal, b.
 [clinic start generated code]*/
 
 static Py_ssize_t
 _operator_countOf_impl(PyObject *module, PyObject *a, PyObject *b)
-/*[clinic end generated code: output=9e1623197daf3382 input=0c3a2656add252db]*/
+/*[clinic end generated code: output=9e1623197daf3382 input=93ea57f170f3f0bb]*/
 {
     return PySequence_Count(a, b);
 }
diff --git a/Modules/clinic/_operator.c.h b/Modules/clinic/_operator.c.h
index 34b6fda..bda2eba 100644
--- a/Modules/clinic/_operator.c.h
+++ b/Modules/clinic/_operator.c.h
@@ -957,7 +957,7 @@ PyDoc_STRVAR(_operator_countOf__doc__,
 "countOf($module, a, b, /)\n"
 "--\n"
 "\n"
-"Return the number of times b occurs in a.");
+"Return the number of items in a which are, or which equal, b.");
 
 #define _OPERATOR_COUNTOF_METHODDEF    \
     {"countOf", (PyCFunction)(void(*)(void))_operator_countOf, METH_FASTCALL, _operator_countOf__doc__},
@@ -1486,4 +1486,4 @@ _operator__compare_digest(PyObject *module, PyObject *const *args, Py_ssize_t na
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=eae5d08f971a65fd input=a9049054013a1b77]*/
+/*[clinic end generated code: output=16749e11fda51785 input=a9049054013a1b77]*/