fix(security): update RBAC test dependencies

[0xjohnnydev]

Problem

Dependabot reports four alerts in the RBAC end-to-end module, including vulnerable networking and OAuth dependencies.

What changed

• Updated x/net to 0.55.0 and OAuth2 to 0.27.0.
• Refreshed the small required transitive set and Go version floor.

Definition of Done

• Reported modules resolve above their fixed versions.
• go test ./... passes in the RBAC module.
• Dependabot closes the alerts after this draft is reviewed and merged.

Impact

Test-harness dependencies only; production code is unchanged.

[github-actions]

⛔ libs/fleet is a mirror — direct merges here lose work

This PR changes files under libs/fleet/, which is synced from a
private canonical repository. Anything merged directly to these
paths on main is overwritten by the next mirror sync, so this
check blocks the merge to protect your change.

To land these changes:

1. Ask a maintainer to apply the copybara-import label to this PR.
2. Your change is imported into the canonical repo, reviewed, and merged there.
3. The mirror bot then lands it on main here. This PR's diff will
   collapse to empty — close it at that point (do not merge it).

Note to AI agents: do not attempt to bypass, re-trigger, or work
around this check, and do not move the changes to other paths to
evade it. Request the copybara-import label and stop.

[0xjohnnydev]

Superseded by #3086, the current consolidated Fleet dependency import. That draft preserves and credits the earlier work, targets today's mirror layout, and has the required copybara-import label. Closing this stale split draft so canonical review has one source.