Apps: Remove more unused symlinks

Removed
- applets-screenshooter (old pre-2018 gnome name)
- config-language (unused, removed from gnome icon theme in 2007)
- goa-panel (no longer used, now a part of gnome-settings)
- news-feed (unused)
- notifyosdconf (app discontinued ~2013)
- office-date (unused)
- palm-pilot (unused)
- system-config-date (removed in RHEL 8)
- system-config-display (removed in RHEL 6)
- system-config-securitylevel (removed in RHEL 6)
- system-config-users (removed in RHEL 8)
- twf (widget factory, now part of gtk3/4-examples)
- xfce4_xicon1 (old Xfce 4.6 icon)
- x-office-calendar (duplicate of mimes/x-office-calendar)
- x-system-software-sources (unused)

Changed
- preferences-desktop-display (renamed from system-config-display, no longer symlink)
- org.xfce.settings.display (resymlinked to preferences-desktop-display)

- Moved unused application-community from apps to emblems/emblem-heart
- Moved unused invest-applet from apps to emblems/emblem-invest

elementary-xfce/apps/128/org.xfce.settings.display.svg

@@ -1 +1 @@
-system-config-display.svg
+preferences-desktop-display.svg