[gparted] Remain with CentOS 7 for GitLab CI (!48)

[Curtis Gedak <gedakc src gnome org>]

commit 22984637b06e9fba2f93cde66572017b596bc0c9
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Sun Sep 29 10:13:49 2019 +0100

    Remain with CentOS 7 for GitLab CI (!48)
    
    When GParted GitLab Continuous Integration was setup, CentOS 7 image was
    used for a slow moving distribution and Ubuntu as a different, faster
    moving distribution.
    
    CentOS 8 has recently been released [1].  To avoid automatically
    switching to it when an official CentOS 8 docker image is made available
    [2], explicitly specify the CentOS 7 image.
    
    [1] Release for CentOS Linux 8 and CentOS Streams (2019-09-24)
        https://lists.centos.org/pipermail/centos-announce/2019-September/023449.html
    
    [2] Docker Official Images, The official build of CentOS
        https://hub.docker.com/_/centos/
    
    Closes !48 - Remain with CentOS 7 for GitLab CI

 .gitlab-ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 4384c197..855dfb3f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -4,7 +4,7 @@ stages:
 
 .centos_image_template: &centos_image_definition
   # Use official CentOS image https://hub.docker.com/_/centos/.
-  image: centos:latest
+  image: centos:centos7
   before_script:
     - yum update -y
     - yum install -y which gnome-common yelp-tools glib2-devel intltool