chore(deps): update griefed/baseimage-ubuntu-jdk-8 docker tag to v2.0.15

.gitlab-ci.yml

@@ -21,7 +21,7 @@ workflow:
     - when: always
 
 Gradle Test:
-  image: griefed/baseimage-ubuntu-jdk-8:2.0.14
+  image: griefed/baseimage-ubuntu-jdk-8:2.0.15
   stage: Gradle Test
   before_script:
     - echo "**** Running in $CI_JOB_ID ****"
@@ -63,7 +63,7 @@ Release:
     - if: '$CI_COMMIT_BRANCH == "main" && $CI_COMMIT_TITLE !~ /^RELEASE:.+$/ && $CI_SERVER_HOST == "git.griefed.de"'
 
 pages:
-  image: griefed/baseimage-ubuntu-jdk-8:2.0.14
+  image: griefed/baseimage-ubuntu-jdk-8:2.0.15
   stage: Documentation
   before_script:
     - which java