chore: updating automation to use librarian 0.5.0 (#2655)

https://github.com/googleapis/librarian/releases/tag/v0.5.0

Author: ldetmer

infra/prod/generate.yaml

@@ -47,7 +47,7 @@ steps:
       - '--single-branch'
       - '--branch=master'
       - https://github.com/googleapis/googleapis
-  - name: 'us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/librarian'
+  - name: 'us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/librarian@sha256:5a001095dcee6b6fdaf3f826a4a339853786b55b21f571daefdfffa995e01272'
     id: generate
     waitFor: ['configure-language-repo-email', 'clone-googleapis']
     dir: tmp

infra/prod/publish-release.yaml

@@ -26,7 +26,7 @@ steps:
       - '--single-branch'
       - '--branch=$_BRANCH'
       - $_FULL_REPOSITORY
-  - name: 'us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/librarian'
+  - name: 'us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/librarian@sha256:5a001095dcee6b6fdaf3f826a4a339853786b55b21f571daefdfffa995e01272'
     id: publish-release
     waitFor: ['clone-language-repo']
     args:

infra/prod/stage-release.yaml

@@ -41,7 +41,7 @@ steps:
       - 'config'
       - 'user.email'
       - '[email protected]'
-  - name: 'us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/librarian'
+  - name: 'us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/librarian@sha256:5a001095dcee6b6fdaf3f826a4a339853786b55b21f571daefdfffa995e01272'
     id: stage-release
     waitFor: ['configure-language-repo-email']
     dir: tmp