bug#65156: 29.1; Reading from pipe with --insert or insert-file-contents no longer supported

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

> WDYT about backporting this (both the doc string and the erasing fix)
> to emacs-29?

That's not necessary, since `if-regular' doesn't exist on Emacs 29; it's
used in Emacs 30 to ``visit'' non-regular files as files.

I sincerely apologize for causing this mess.