Remove unused code in `_pyrepl.windows_console.py`

[tanloong]

In windows_console.py, there are some unused code that were left there when porting from unix_console.py:

• px_pos and self.__gone_tall are defined but not used.
• Comment about self.dch1 is misleading as there is no self.dch1 in windows_console.py.

Linked PRs

• gh-141415: Remove unused variables and comment in _pyrepl.windows_console.py #141416