Update .gitlab-ci.yml

.gitlab-ci.yml

 include:
   - "https://git.autistici.org/ai3/build-container/raw/master/common.yml"
-  - "https://git.autistici.org/ai3/build-deb/raw/master/ci-nextstable.yml"
+  - "https://git.autistici.org/ai3/build-deb/raw/master/ci-common.yml"
 
 stages:
   - test