use custom environment for publishing crates (paritytech#12912)

Author: joao-paulo-parity

scripts/ci/gitlab/pipeline/publish.yml

@@ -211,6 +211,9 @@ update-node-template:
   # to roughly 202 minutes of delay, or 3h and 22 minutes. As such, the job needs to have a much
   # higher timeout than average.
   timeout:                         5h
+  # A custom publishing environment is used for us to be able to set up protected secrets
+  # specifically for it
+  environment: publish-crates
   script:
     - rusty-cachier snapshot create
     - git clone