Fix incorrect error message for ctypes bitfield overflow.

The previous message did not match the actual overflow check and omitted
the bitfield size, making it misleading. Update the message to reflect the
correct condition and report all relevant values.

Signed-off-by: Yongtao Huang <yongtaoh2022@gmail.com>

Author: hyongtao-code

Modules/_ctypes/cfield.c

@@ -160,8 +160,8 @@ PyCField_new_impl(PyTypeObject *type, PyObject *name, PyObject *proto,
         if ((bitfield_size + bit_offset) > byte_size * 8) {
             PyErr_Format(
                 PyExc_ValueError,
-                "bit field %R overflows its type (%zd + %zd >= %zd)",
-                name, bit_offset, byte_size*8);
+                "bit field %R overflows its type (%zd + %zd > %zd)",
+                name, bit_offset, bitfield_size, byte_size * 8);
             goto error;
         }
     }