Delete docker imnage before building new one

The images seem to remain on the runner machine.

Change-Id: Idac237b2464c1f22da3f1440304cf53443c60571
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 37fb414..ea6a3a2 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -50,6 +50,7 @@
     - apk update
     - apk add --no-cache git
   script:
+    - docker rm --force /corpuscomposition
     - docker build -f Dockerfile -t korap/corpuscomposition:$VID .
     - docker run -d --name corpuscomposition korap/corpuscomposition:$VID
     - docker cp corpuscomposition:/cache ./