[evince] ci: install gi-docgen for the CI image

[Germán Poo-Caamaño <gpoo src gnome org>]

commit 4eda0cc5847d1266c9c519033cc1738e39e63a9b
Author: Qiu Wenbo <qiuwenbo kylinos com cn>
Date:   Thu Dec 2 09:54:15 2021 +0800

    ci: install gi-docgen for the CI image
    
    Signed-off-by: Qiu Wenbo <qiuwenbo kylinos com cn>

 .gitlab-ci/setup-ubuntu.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.gitlab-ci/setup-ubuntu.sh b/.gitlab-ci/setup-ubuntu.sh
index e1d53c341..7be3eec63 100644
--- a/.gitlab-ci/setup-ubuntu.sh
+++ b/.gitlab-ci/setup-ubuntu.sh
@@ -22,6 +22,6 @@ apt-get -yq install gnome-common libglib2.0-dev-bin \
 apt-get clean
 rm -rf /var/lib/apt/lists/*
 
-pip3 install meson
+pip3 install meson gi-docgen
 
 useradd -u 1984 -ms /bin/bash user