docs(github): correct action token configuration

[neriousy]

Summary

• remove the stale legacy token documentation and never-valid github_token example
• document the current mentions, variant, oidc_base_url, and use_github_token inputs
• show a complete caller-token configuration and clarify that OIDC permission is unnecessary in that mode
• fix the malformed indentation in the manual workflow example

The legacy token input was removed when the action switched to opencode github run; #5459 subsequently established use_github_token plus the GITHUB_TOKEN environment variable as the supported replacement.

Supersedes #44668. Thanks @harshil-mistry for identifying the stale input documentation.

Verification

• Prettier
• git diff --check
• full workspace typecheck from the pre-push hook (30/30 tasks)

Fixes#44667