[gnome-flashback] ci: use ubuntu 21.04 image

[Alberts Muktupāvels <muktupavels src gnome org>]

commit be30a4efed27ec4ab518deeea4516606cc309bde
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Thu May 13 19:48:09 2021 +0300

    ci: use ubuntu 21.04 image

 .gitlab-ci.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a57c513..ec8b937 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -46,7 +46,7 @@ variables:
                   xkb-data
 
 menu:
-  image: ubuntu:devel
+  image: ubuntu:hirsute
   stage: validate
   except:
     - tags
@@ -59,7 +59,7 @@ menu:
       data/menus/gnome-flashback-applications.menu
 
 ubuntu:
-  image: ubuntu:devel
+  image: ubuntu:hirsute
   stage: build
   except:
     - tags
@@ -72,7 +72,7 @@ ubuntu:
     - make distcheck
 
 coverity:
-  image: ubuntu:devel
+  image: ubuntu:hirsute
   stage: analysis
   when: manual
   before_script: