glx: Fix drawable type inference in visual/fbconfig setup

glx: Fix drawable type inference in visual/fbconfig setup

This was just all kinds of wrong. Note that the comment implying "this
is a workaround for old XQuartz" is on the "not apple" side of the
ifdef. Anyway. xserver didn't start sending GLX_DRAWABLE_TYPE in the
fbconfig until:

    commit 8cde0af3c57f0375ba8ba77af9fdf74b79d9496d
    Author: Kristian Høgsberg <krh@redhat.com>
    Date:   Wed Apr 2 19:06:40 2008 -0400

        Send the GLX_EXT_texture_from_pixmap attributes to the client.

So we can remove this default from the fbconfig path. But we preserve it
for the GLXGetVisualConfigs path, because that is specified not to send
GLX_DRAWABLE_TYPE.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20549>