build: Switch Docker image to Debian bullseye
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 3697f19..e6aafdb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,4 +1,4 @@
-image: debian:buster
+image: debian:bullseye
before_script:
- apt-get update -qq