bpo-29852: Argument Clinic Py_ssize_t converter now supports None (#716)

if pass `accept={int, NoneType}`.
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
index 6000508..3c0b752 100644
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -52,13 +52,6 @@
 [clinic start generated code]*/
 /*[clinic end generated code: output=da39a3ee5e6b4b0d input=1c77708b41fda70c]*/
 
-/*[python input]
-class io_ssize_t_converter(CConverter):
-    type = 'Py_ssize_t'
-    converter = '_PyIO_ConvertSsize_t'
-[python start generated code]*/
-/*[python end generated code: output=da39a3ee5e6b4b0d input=d0a811d3cbfd1b33]*/
-
 typedef struct {
     PyObject_HEAD
     int fd;
@@ -770,7 +763,7 @@
 
 /*[clinic input]
 _io.FileIO.read
-    size: io_ssize_t = -1
+    size: Py_ssize_t(accept={int, NoneType}) = -1
     /
 
 Read at most size bytes, returned as bytes.
@@ -782,7 +775,7 @@
 
 static PyObject *
 _io_FileIO_read_impl(fileio *self, Py_ssize_t size)
-/*[clinic end generated code: output=42528d39dd0ca641 input=5c6caa5490c13a9b]*/
+/*[clinic end generated code: output=42528d39dd0ca641 input=bec9a2c704ddcbc9]*/
 {
     char *ptr;
     Py_ssize_t n;