Update Scala CI template to reference openjdk Docker img

doc/ci/examples/test-scala-application.md

@@ -14,7 +14,7 @@ The following `.gitlab-ci.yml` should be added in the root of your
 repository to trigger CI:
 
 ``` yaml
-image: java:8
+image: openjdk:8
 
 stages:
   - test

lib/gitlab/ci/templates/Scala.gitlab-ci.yml

-# Official Java image. Look for the different tagged releases at
-# https://hub.docker.com/r/library/java/tags/ . A Java image is not required
+# Official OpenJDK Java image. Look for the different tagged releases at
+# https://hub.docker.com/_/openjdk/ . A Java image is not required
 # but an image with a JVM speeds up the build a bit.
-image: java:8
+image: openjdk:8
 
 before_script:
   # Enable the usage of sources over https