Fix scratch bucket env vars properly

- GCS storage protocol is gs, not gcs
- Just hardcode the bucket name here, as env var substitution
  relies on ordering of env vars and that is just a bit messy.

config/clusters/leap/common.values.yaml

@@ -60,12 +60,9 @@ basehub:
         name: pangeo/pangeo-notebook
         tag: 2022.02.04
       extraEnv:
-        SCRATCH_BUCKET_PROTOCOL: gcs
-        # Created via terraform
-        SCRATCH_BUCKET_NAME: leap-pangeo-scratch
-        # Use k8s syntax of $(ENV_VAR) to substitute env vars dynamically in other env vars
-        SCRATCH_BUCKET: "{bucket_protocol}://{bucket_name}/$(JUPYTERHUB_USER)"
-        PANGEO_SCRATCH: "{bucket_protocol}://{bucket_name}/$(JUPYTERHUB_USER)"
+        # This bucket is created by terraform
+        SCRATCH_BUCKET: "gs://leap-pangeo-scratch/$(JUPYTERHUB_USER)"
+        PANGEO_SCRATCH: "gs://leap-pangeo-scratch/$(JUPYTERHUB_USER)"
       profileList:
         # The mem-guarantees are here so k8s doesn't schedule other pods
         # on these nodes. They need to be just under total allocatable