This example has been causing on-and-off build breaks for quite some
time.  In this case, the code for copying the generated content into the
main docs of GIO is causing problems with srcdir != destdir builds (due
to the files also being copied from the read-only srcdir during
distchecks).

We could probably work around this problem yet again, but since there is
no real benefit to having this content included, so let's remove it.

https://bugzilla.gnome.org/show_bug.cgi?id=734469