bpo-34580: Update sqlite3 examples to call close() explicitly (GH-9079)

The sqlit3.Connection object doesn't call its close() method when it's used
as a context manager.
diff --git a/Doc/includes/sqlite3/executescript.py b/Doc/includes/sqlite3/executescript.py
index 7e53581..aea8943 100644
--- a/Doc/includes/sqlite3/executescript.py
+++ b/Doc/includes/sqlite3/executescript.py
@@ -22,3 +22,4 @@
         1987
     );
     """)
+con.close()