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/cache.h b/Modules/_sqlite/cache.h
index a133903..5290109 100644
--- a/Modules/_sqlite/cache.h
+++ b/Modules/_sqlite/cache.h
@@ -23,6 +23,7 @@
 
 #ifndef PYSQLITE_CACHE_H
 #define PYSQLITE_CACHE_H
+#define PY_SSIZE_T_CLEAN
 #include "Python.h"
 
 /* The LRU cache is implemented as a combination of a doubly-linked with a