info-overview: rename "GNOME Version" to "GNOME Shell Version"

The GNOME version and the GNOME Shell version are not the same thing. Historically, this panel displayed the GNOME version from gnome-desktop. But that is not very useful, so for GNOME 43 we switched to showing the GNOME Shell version instead. Now that GNOME 43.1 is out but GNOME Shell 43.1 is not, users are noticing the inconsistency between the version numbers. It's too late to fix for GNOME 43 due to string freeze, but we should disambiguate this going forward.