Use native readline function for new history file

[ItsDrike]

In commit 07bcbe5 an issue described in python/cpython#105694 was solved by changing the pythonrc script and adding:

with open(history,\"w\") as f:
    f.write(\"_HiStOrY_V2_\" + \"\\n\\n\") # breaks on macos + python3 without this.

Even though this does indeed solve the issue, it's really ugly code-wise, and there is a built-in way to do this in the readline library, with:

readline.write_history_file(str(history)) # breaks on macos + python3 without this.

This PR just edits the script to use that instead.

[b3nj5m1n]

Thanks!