[codex] RDSC-4454 Document RDI maintenance deletion limit

[ZdravkoDonev-redis]

Summary

• Add a note to the RDI Delete pipeline docs that data pipelines cannot be deleted while the target Redis Cloud cluster is in maintenance mode.
• Tell users to retry deletion after maintenance is complete.

Why

RDSC-4454 exposed the maintenance-mode restriction during RDI pipeline deletion. The docs now call out the limitation in the relevant delete workflow.

Validation

• git diff --check

[github-actions]

Staging links:
https://redis.io/docs/staging/codex/content/operate/rc/databases/rdi/view-edit/

[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

---

^{Security scan by Jit}