Apps: Update Terminal, pull from upstream

Use upstream's newer `utilities-terminal`.

Use former `utilities-terminal` for Xfce Terminal.
Update with newer style rounded-corners, gradients,
semi-transparent borders. It now better matches the
upstream Xfce Terminal icon, and gives people a choice
for different terminal icons.

Fix:
Update `internet-mail` at 16px. Make larger to match other category/app
icons (they should all be the same size in Xfce Applications Menu),
use semi-transparent borders for sharper look on dark themes.

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

@@ -1 +1 @@
-utilities-terminal.svg
+org.xfce.terminal.svg