Update Redis Enterprise openapi spec

[redis-enterprise-doc-sync]

Daily sync found updated API definitions.

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Note

Low Risk
Low risk documentation-only change that updates OpenAPI metadata; no runtime behavior is modified.

Overview
Adds x-timeout-seconds: 900 to the OpenAPI spec for the long-running cluster certificate update endpoints (PUT /v1/cluster/certificates and deprecated PUT /v1/cluster/update_cert), indicating a 15-minute timeout for these operations.

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[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

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^{Security scan by Jit}