gh-126433: Change channel_info.count to int64_t (#126447)

Fix compiler warnings on 32-bit Windows: change channel_info.count
type from Py_ssize_t to int64_t in _interpchannelsmodule.c.

Modules/_interpchannelsmodule.c

@@ -2047,7 +2047,7 @@ struct channel_info {
             int recv;
         } cur;
     } status;
-    Py_ssize_t count;
+    int64_t count;
 };
 
 static int