Fix typo in yaml configuration

git-svn-id: https://subversion.gsi.de/cbmsoft/cbmroot/trunk@15312 5a1b234a-d7ce-0410-9a93-fd649a8fa65c

.gitlab-ci.yml

 stages:
   - build
-
+  - documentation
+  
 CbmRoot_Continuous:
   stage: build
   tags:
@@ -85,7 +86,7 @@ CbmRoot_Continuous:
 #    - $PWD/Dart.sh Nightly Dart.cfg
 
 pages:
-  stage: build
+  stage: documentation
   image: alpine
   tags:
     - docker
@@ -97,4 +98,4 @@ pages:
     paths:
       - public
   only:
-    - doxgen
+    - doxygen