xfce4-terminal: update to 0.8.10

Change log:

0.8.10
======
- Bump libvte, gtk and xfce minimal versions (4.14)
- Stop using G_SPAWN_CHILD_INHERITS_STDIN spawn flag
- Updates README.md.
- Added new stock icons
- Limit font picker to fixed-size fonts
- Add gtk-doc as a dependency
- Do not require connection to generate manpage
- Bug #16875: Do not add ui.h file in datadir
- Simplify terminal manpage generation
- Switch preferences ui file to xdt-csource
- Switch to README.md and foreign automake mode
- Do not override clipboard contents
- Unsafe paste: Support bracketed paste mode
- Do not select text in Search dialog
- Add basic GitLab pipeline
- Translation Updates:
  Albanian, Armenian (Armenia), Basque, Bulgarian, Chinese (China),
  Chinese (Taiwan), Danish, Dutch, Eastern Armenian, Estonian, French,
  Greek, Hebrew, Hungarian, Indonesian, Interlingue, Italian, Japanese,
  Lithuanian, Norwegian Bokm奪l, Occitan (post 1500), Polish,
  Portuguese, Portuguese (Brazil), Russian, Serbian, Slovak, Slovenian,
  Spanish, Swedish, Turkish, Ukrainian, Uyghur

(gutteridge)