Use Docker Hub mirror consistently on CI and avoid unneeded log in

Closes gh-31070

ci/pipeline.yml

@@ -13,8 +13,7 @@ anchors:
     GRADLE_ENTERPRISE_CACHE_USERNAME: ((gradle_enterprise_cache_user.username))
     GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
   docker-hub-task-params: &docker-hub-task-params
-    DOCKER_HUB_USERNAME: ((docker-hub-username))
-    DOCKER_HUB_PASSWORD: ((docker-hub-password))
+    DOCKER_HUB_MIRROR: ((docker-hub-mirror))
   github-task-params: &github-task-params
     GITHUB_REPO: spring-boot
     GITHUB_ORGANIZATION: spring-projects

ci/scripts/common.sh

@@ -5,8 +5,4 @@ if [[ -d $PWD/embedmongo && ! -d $HOME/.embedmongo ]]; then
 	ln -s "$PWD/embedmongo" "$HOME/.embedmongo"
 fi
 
-if [[ -n $DOCKER_HUB_USERNAME ]]; then
-	docker login -u $DOCKER_HUB_USERNAME -p $DOCKER_HUB_PASSWORD
-fi
-
 cleanup_maven_repo "org.springframework.boot"