package/transmission: fix gtk dependencies

Buildroot commit 80793107a65d95f8dfd0317a726d3a737c78ef67 forgot to add
packages needed for gtk support:
https://github.com/transmission/transmission/blob/main/CMakeLists.txt#L40

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
[yann.morin.1998@free.fr:
  - don't add dependencies to C++ or wh-char, already global deps
  - propagate sync-4 dependency to comment
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
2 files changed