Python 3.13.0b1 REPL does not deduplicate history entries

Bug report

Bug description:

Consider this:

>>> 1
1
>>> 2
2
>>> 2
2
>>> 2
2
>>> 2
2
>>> 2
2
>>> 2
2
>>>

Now press the arrow up (↑). 2 appears. Then, press it again...

• On Python 3.12, I get 1 after the second ↑ press. I consider this the natural behavior.
• On Python 3.13, I get 1 only after the 7nd ↑ press. I consider this weird.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-119276

使用重複輸入範例，重現 Python 3.12 和 3.13 REPL 中向上箭頭的歷史記錄行為。比較歷史記錄導覽行為，檢視連結的 PR gh-119276 以了解現有工作，並在重複項目如同 Python 3.12 中一樣被跳過時將 issue 視為完成。