[3.13] gh-141732: Fix ExceptionGroup repr changing when original exception sequence is mutated (GH-141736) (#142391)

* [3.13] gh-141732: Fix `ExceptionGroup` repr changing when original exception sequence is mutated (GH-141736)
(cherry picked from commit ff2577f56eb2170ef0afafa90f78c693df7ca562)

Co-authored-by: dr-carlos <77367421+dr-carlos@users.noreply.github.com>