*/*: restore ~ia64 gnome-base/gnome-shell keywords

*/*: restore ~ia64 gnome-base/gnome-shell keywords

Émeric Maschino and Mart Raudsepp noted that
gnome-extra/evolution-data-server has no hard dependency
on webkit-gtk and we can just mask USE=oauth there.

This change does exactly that and restores keywords
for the following packages:

- gnome-base/gdm
- gnome-base/gnome-shell
- nome-extra/chrome-gnome-shell
- nome-extra/evolution-data-server

Reported-by: Émeric Maschino
Closes: https://bugs.gentoo.org/717550
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>