Fix corfu-popupinfo-mode

[skissue]

By default, corfu-popupinfo-mode's popup window appears as a new frame rather than a proper popup. Adding corfu-popupinfo--show to the list of functions to ignore seems to fix the issue.

Not sure if this is the best way to solve it, or if frames-only-mode-use-window-functions is intended to have broad defaults, so feel free to close this PR if functions like these should be left to user configuration.