[3.7] Fix misleading mentions of tp_size in comments. (GH-9136)

Many type object initializations labeled a field "tp_size" in the
comment, but the name of that field is tp_basicsize..
(cherry picked from commit 0e0bc4e221f592f305d335faf5f8046484eb9238)

Co-authored-by: Peter Eisentraut <peter@eisentraut.org>
diff --git a/Modules/_sha3/sha3module.c b/Modules/_sha3/sha3module.c
index f73bc99..d879e92 100644
--- a/Modules/_sha3/sha3module.c
+++ b/Modules/_sha3/sha3module.c
@@ -489,7 +489,7 @@
     static PyTypeObject type_obj = { \
         PyVarObject_HEAD_INIT(NULL, 0) \
         type_name,          /* tp_name */ \
-        sizeof(SHA3object), /* tp_size */ \
+        sizeof(SHA3object), /* tp_basicsize */ \
         0,                  /* tp_itemsize */ \
         /*  methods  */ \
         (destructor)SHA3_dealloc, /* tp_dealloc */ \