When "org.gnome.desktop.a11y.applications screen-reader-enabled" or
"org.gnome.desktop.a11y.applications screen-keyboard-enabled" get
enabled, we should set the
"org.gnome.desktop.interface toolkit-accessibility" key.

This is because the universal access UI will not offer a checkbox to set
just the accessibility settings.

https://bugzilla.gnome.org/show_bug.cgi?id=642596