Fix release pipeline for Maven Central publication

This commit fixes the missing pieces in our Maven Central publication
pipeline. Our first attempt at releasing with it showed a few problems:

* the promote task did not have the artifacts downladed with the
  artifactory repository
* we applied the wrong Sonatype credentials to the task
* the github changelog task would fail because of docker rate limiting
  since we were not using the right type of resource, which is
  configured with the proper caching mechanism

See spring-projectsgh-26654

ci/images/setup.sh

@@ -14,7 +14,7 @@ rm -rf /var/lib/apt/lists/*
 
 curl https://raw.githubusercontent.com/spring-io/concourse-java-scripts/v0.0.4/concourse-java.sh > /opt/concourse-java.sh
 
-curl --output /opt/concourse-release-scripts.jar https://repo.spring.io/release/io/spring/concourse/releasescripts/concourse-release-scripts/0.3.0/concourse-release-scripts-0.3.0.jar
+curl --output /opt/concourse-release-scripts.jar https://repo.spring.io/release/io/spring/concourse/releasescripts/concourse-release-scripts/0.3.1/concourse-release-scripts-0.3.1.jar
 
 ###########################################################
 # JAVA

ci/pipeline.yml

@@ -9,8 +9,8 @@ anchors:
     GRADLE_ENTERPRISE_CACHE_USERNAME: ((gradle_enterprise_cache_user.username))
     GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
   sonatype-task-params: &sonatype-task-params
-    SONATYPE_USER_TOKEN: ((sonatype-user-token))
-    SONATYPE_PASSWORD_TOKEN: ((sonatype-user-token-password))
+    SONATYPE_USERNAME: ((sonatype-username))
+    SONATYPE_PASSWORD: ((sonatype-password))
     SONATYPE_URL: ((sonatype-url))
     SONATYPE_STAGING_PROFILE_ID: ((sonatype-staging-profile-id))
   artifactory-task-params: &artifactory-task-params
@@ -348,7 +348,7 @@ jobs:
       trigger: false
       passed: [stage-release]
       params:
-        download_artifacts: false
+        download_artifacts: true
         save_build_info: true
     - task: promote
       image: ci-image

ci/tasks/generate-changelog.yml

@@ -1,7 +1,7 @@
 ---
 platform: linux
 image_resource:
-  type: docker-image
+  type: registry-image
   source:
     repository: springio/github-changelog-generator
     tag: '0.0.6'

ci/tasks/promote-version.yml

@@ -10,8 +10,8 @@ params:
   ARTIFACTORY_SERVER:
   ARTIFACTORY_USERNAME:
   ARTIFACTORY_PASSWORD:
-  SONATYPE_USER_TOKEN:
-  SONATYPE_PASSWORD_TOKEN:
+  SONATYPE_USER:
+  SONATYPE_PASSWORD:
   SONATYPE_URL:
   SONATYPE_STAGING_PROFILE_ID:
 run: