fix yml syntax

.gitlab-ci.yml

@@ -2,7 +2,7 @@ stages:
   - build
   - deploy
 
-retrieve repo:
+retrieve:repo:
   image:
     name: alpine/git:latest
     entrypoint: [""]
@@ -14,21 +14,21 @@ retrieve repo:
     paths:
       - courses.lcsb.uni.lu
 
-build index:
+build:index:
   image: python
   stage: build
   dependencies:
-    - courses.lcsb.uni.lu
+    - retrieve:repo
   rules:
     - if: $CI_COMMIT_BRANCH == "develop"
   script:
     - python .ci/generateIndex.py
 
-build the website:
+build:website:
   image: git-r3lab.uni.lu:4567/r3/docker/jekyll-lcsb:1.4
   stage: build
   dependencies:
-    - courses.lcsb.uni.lu
+    - retrieve:repo
   before_script:
     - cd courses.lcsb.uni.lu
     - gem install bundler -v2.0.2
@@ -45,7 +45,7 @@ build the website:
   variables:
     JEKYLL_ENV: production
 
-build courses:
+build:courses:
   image: git-r3lab.uni.lu:4567/r3/docker/nodejs-yarn-grunt
   stage: build
   rules: