chore: remove librarian repository from automation (#2892)

In order to reduce support as we make changes to librarian CLI, let's
remove Librarian project from automation. We will no longer use it as
dogfood until we have upgraded to the new CLI.

Signed-off-by: ldetmer <1771267+ldetmer@users.noreply.github.com>

Author: ldetmer

internal/automation/prod/repositories.yaml

@@ -13,12 +13,6 @@ repositories:
       - generate
       - stage-release
       - publish-release
-  - name: "librarian"
-    full-name: https://github.com/googleapis/librarian
-    github-token-secret-name: "librarian-github-token"
-    supported-commands:
-      - stage-release
-      - publish-release
   - name: "gax-go"
     full-name: https://github.com/googleapis/gax-go
     github-token-secret-name: "gax-go-github-token"