Fix off-by-one error in SQL length limit check (RustPython#5982)

Author: ever0de

Lib/test/test_sqlite3/test_regression.py

@@ -349,8 +349,6 @@ def test_surrogates(self):
         self.assertRaises(UnicodeEncodeError, cur.execute, "select '\ud8ff'")
         self.assertRaises(UnicodeEncodeError, cur.execute, "select '\udcff'")
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_large_sql(self):
         msg = "query string is too large"
         with memory_database() as cx, cx_limit(cx) as lim:

stdlib/src/sqlite.rs

@@ -2309,11 +2309,10 @@ mod _sqlite {
                 ));
             }
             let sql_cstr = sql.to_cstring(vm)?;
-            let sql_len = sql.byte_len() + 1;
 
             let db = connection.db_lock(vm)?;
 
-            db.sql_limit(sql_len, vm)?;
+            db.sql_limit(sql.byte_len(), vm)?;
 
             let mut tail = null();
             let st = db.prepare(sql_cstr.as_ptr(), &mut tail, vm)?;