bug#48375: coding-system-for-read in net-utils-run-simple is not properly set

[iquiw]

In the following code, `let' binding of `coding-system-for-read'
covers only `erase-buffer' call.

https://emba.gnu.org/emacs/emacs/-/blob/47070ed39eda524d334e5f82dc7f4a50b8d3252c/lisp/net/net-utils.el#L366-375

So it does not affect to executed process and output characters are garbled.
e.g. "M-x ifconfig" on Windows.

`net-utils-run-program' (e.g. "M-x ping") has no problem.

Thanks in advance,
Iku