gitlab: Remove temporary storage url from all stacks (#29949)

Gitlab pipelines run for spack already have other S3 storage locations
configured for storage of binaries, so this PR removes the redundant
per-pipeline mirror.  As a result, the "cleanup" jobs will no longer be
generated at the end of each pipeline, removing one possible point of
pipeline failure.

share/spack/gitlab/cloud_pipelines/stacks/tutorial/spack.yaml

@@ -134,7 +134,7 @@ spack:
           tags: ["spack", "public", "x86_64"]
           variables:
             CI_JOB_SIZE: default
-    temporary-storage-url-prefix: "s3://spack-binaries-prs/pipeline-storage"
+
     broken-specs-url: "s3://spack-binaries-develop/broken-specs"
     service-job-attributes:
       image: { "name": "ghcr.io/spack/tutorial-ubuntu-18.04:v2021-11-02", "entrypoint": [""] }
@@ -143,7 +143,6 @@ spack:
         - spack --version
       tags: ["spack", "public", "x86_64"]
 
-
   cdash:
     build-group: Spack Tutorial
     url: https://cdash.spack.io