gh-140939: Fix memory leak in _PyBytes_FormatEx error path

[StanFromIreland]

It is already accounted for in the other path:

cpython/Objects/bytesobject.c

Lines 1049 to 1054 in b373d34

	if (dict && (argidx < arglen)) {
	PyErr_SetString(PyExc_TypeError,
	"not all arguments converted during bytes formatting");
	Py_XDECREF(temp);
	goto error;
	}

• Issue: memory leak in _PyPegen_constant_from_string #140939