bpo-8677: use PY_SSIZE_T_CLEAN in sqlite (GH-12434)

Modules/_sqlite/cursor.c uses "y#" format.
It didn't declare PY_SSIZE_T_CLEAN, but the argument is Py_ssize_t already.
diff --git a/Modules/_sqlite/module.h b/Modules/_sqlite/module.h
index 6f90934..3185ec9 100644
--- a/Modules/_sqlite/module.h
+++ b/Modules/_sqlite/module.h
@@ -23,6 +23,7 @@
 
 #ifndef PYSQLITE_MODULE_H
 #define PYSQLITE_MODULE_H
+#define PY_SSIZE_T_CLEAN
 #include "Python.h"
 
 #define PYSQLITE_VERSION "2.6.0"