main/waydroid-image: remove

This has been out-of-date for almost a year with seemingly stalled progress on the existing upgrade MR (!3091 (closed)) for months now; it really seems like no one wants to maintain this which currently leaves this "force-installed-by-default" packaged image broken on all wlroots-based Wayland compositors for example as it stands which users have also started to report (#1653 (closed)).

I previously added the echo !waydroid-image >> /etc/apk/world tip on https://wiki.postmarketos.org/wiki/Waydroid#Installation but if everyone needs to do that to use Waydroid why should this package even exist?

Another solution could be to simply remove the install_if="waydroid" which currently makes this image "forced" on users that install waydroid without messing with /etc/apk/world as mentioned above. Without the install_if the docs could be updated to simply say the following instead and imho it wouldn't be a problem:

$ sudo apk add waydroid waydroid-image

Cc. @Newbyte (who I already talked with about this previously and the response to should the package be removed was I don't think so. The default image should be good enough for most people, and I think it is more intuitive if the default image gets installed automatically)