Remove Slack "here" mentions for failed builds

This was introduced by mistake in 6b978cb5

ci/pipeline.yml

@@ -18,7 +18,7 @@ anchors:
     GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
   slack-fail-params: &slack-fail-params
     text: >
-      :concourse-failed: <!here> <https://ci.spring.io/teams/${BUILD_TEAM_NAME}/pipelines/${BUILD_PIPELINE_NAME}/jobs/${BUILD_JOB_NAME}/builds/${BUILD_NAME}|${BUILD_PIPELINE_NAME} ${BUILD_JOB_NAME} failed!>
+      :concourse-failed: <https://ci.spring.io/teams/${BUILD_TEAM_NAME}/pipelines/${BUILD_PIPELINE_NAME}/jobs/${BUILD_JOB_NAME}/builds/${BUILD_NAME}|${BUILD_PIPELINE_NAME} ${BUILD_JOB_NAME} failed!>
       [$TEXT_FILE_CONTENT]
     text_file: git-repo/build/build-scan-uri.txt
     silent: true