[glibmm] .gitlab-ci.yml: Add dependency g++-10

[Kjell Ahlstedt <kjellahl src gnome org>]

commit f8ce50a0668be29582232580acbe0a4dca6496a8
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Tue Aug 17 17:30:34 2021 +0200

    .gitlab-ci.yml: Add dependency g++-10

 .gitlab-ci.yml | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 2d9d0f17..24635b94 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -9,6 +9,7 @@ stages:
 variables:
   DEPENDENCIES: g++
                 g++-9
+                g++-10
                 gettext
                 git
                 yelp-tools