[nautilus] CI: Add ruby image for the triage job

[Carlos Soriano <csoriano src gnome org>]

commit 5523d0296903ac1037dc7e0eaa10ea5f38a902f2
Author: Carlos Soriano <csoriano1618 gmail com>
Date:   Fri Dec 14 13:26:18 2018 +0000

    CI: Add ruby image for the triage job

 .gitlab-ci.yml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 8eded2562..35037086e 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -185,6 +185,7 @@ pages:
     - master
 
 triage:
+  image: ruby:2.4
   stage: triage
   script:
     - gem install gitlab-triage
@@ -193,6 +194,7 @@ triage:
     - schedules
 
 triage:dry-run:
+  image: ruby:2.4
   stage: triage
   script:
     - gem install gitlab-triage