Fix the release pipeline

The build base image task has been removed from the release pipeline
however a dependency to it was left, which breaks the pipeline.

Run the image build and publish after unit and build tests have been
executed.

Signed-off-by: Andrea Frittoli <andrea.frittoli@uk.ibm.com>

tekton/release-pipeline.yaml

@@ -105,7 +105,7 @@ spec:
           workspace: workarea
           subpath: git
     - name: publish-images
-      runAfter: [build-base-image]
+      runAfter: [unit-tests, build]
       taskRef:
         name: publish-release
       params: