Mark INSTALLS_EGGINFO as unsupported

[mva]

Summary

audio/py-pylast was the last port actively using INSTALLS_EGGINFO. Python
support for math/vtk5 is broken, so it can be ignored.

[gahr]

Please give me a couple of days to fix vtk5 before you get this in. I'd really like to get python support working again.

[mva]

In D843#4, @gahr wrote:

Please give me a couple of days to fix vtk5 before you get this in. I'd really like to get python support working again.

INSTALLS_EGGINFO has to vanish anyways, so you have to get rid of it. This is just to calm portlint, qa checks and other things and
to let you know, that it is not supported anymore. Shall I wait nevertheless?

[gahr]

Well go ahead then

[mva]

Committed in rP369800.