Fix test

Author: qyryq

ydb/core/viewer/tests/test.py

@@ -620,7 +620,7 @@ def write(writer, message_pattern, close=True):
         'path': '{}/topic1'.format(dedicated_db),
         'partition': '0',
         'offset': '0',
-        'last_offset': '2',
+        'last_offset': '3',
         'limit': '5'
     })