gh-145394: Remove duplicated isearch_add_character in _pyrepl/historical_reader.py (#145396)

Author: tanloong

Lib/_pyrepl/historical_reader.py

@@ -241,7 +241,6 @@ def __post_init__(self) -> None:
             isearch_end,
             isearch_add_character,
             isearch_cancel,
-            isearch_add_character,
             isearch_backspace,
             isearch_forwards,
             isearch_backwards,