feat(gen): release-please workflow passes GitHub App secrets

[fiunchinho]

Summary

Update the release_please.yaml.template so the generated release-please.yaml workflow in consumer repos passes the new GitHub App secrets (RELEASE_PLEASE_CLIENT_ID, RELEASE_PLEASE_PRIVATE_KEY) to the giantswarm/github-workflows release.yaml reusable workflow, instead of the old TAYLORBOT_GITHUB_ACTION PAT.

This is the consumer-side follow-up to giantswarm/github-workflows#181, which switched the reusable workflow's authentication to a GitHub App token minted via actions/create-github-app-token (client-id: input).

Why

• The reusable workflow now mints a short-lived installation token from a GitHub App, so consumers must pass App credentials, not a PAT.
• Both RELEASE_PLEASE_CLIENT_ID and RELEASE_PLEASE_PRIVATE_KEY are organization-level secrets accessible to all repositories.
• The convention of explicitly passing each secret matches sibling templates like fix_vulnerabilities.yaml.template.

Scope

Only release_please.yaml.template is updated. Other templates (create_release, create_release_pr, update_chart) still pass TAYLORBOT_GITHUB_ACTION because the reusable workflows they call have not migrated yet.

Sequencing

1. Merge feat(release): authenticate release-please via GitHub App github-workflows#181 first.
2. Then merge this PR.
3. Then cut a devctl release and regenerate release-please.yaml in each consumer repo (devctl gen workflows --release-workflow=release-please).

If this PR is merged before #181, repos regenerated in the window will fail their release workflow until #181 lands.

Test plan

• Run devctl gen workflows --release-workflow=release-please against a scratch repo and confirm the generated .github/workflows/release-please.yaml passes RELEASE_PLEASE_CLIENT_ID and RELEASE_PLEASE_PRIVATE_KEY and no longer references TAYLORBOT_GITHUB_ACTION.
• After both this PR and Set version flag in generated Makefiles #181 are merged, regenerate against one low-risk consumer repo and confirm a conventional commit on main produces a release PR opened by the GitHub App.

[fiunchinho]

Superseeded by #1847