gluebuddy: Add gitlab project bot for the arch-boxes project

This will be used for deleting old packages (i.e. the fortnightly
packages which are older than 90 days). I thought using a job token
would work (as described in [1]), but that turned out not to be the case
as explained in [2].

[1] 242213b2 ("gluebuddy: Remove deleted project bot for arch-boxes")
[2] arch-boxes@48ccb457

roles/gluebuddy/defaults/main.yml

@@ -13,3 +13,4 @@ gitlab_bots:
   - project_32147_bot_17ab98ea29bb8d2f93c685af009e3376
   - project_84858_bot_e982c0734ca839275298899e49ed1f51
   - project_10177_bot_5b2d333786a259642a61351696877bae
+  - project_10177_bot_a8dd89a4bf249d4b5d3ec1c3d46e8caf