Fix k8s supported distributions tables and architecture Lifecycle section

[kaitlynmichael]

Fixes found while reviewing the release-k8s-cancun2 branch (PRs #3009 and #3061).

Changes

content/operate/kubernetes/reference/supported_k8s_distributions.md

• Replace the 8.0.18-tbd placeholder with 8.0.18-8 in all 8 tables to match the operator version documented in k8s api docs 8.0.18-8 #3061.
• Restore the newline between {{<table-scrollable>}} and the first table row in the OpenShift, EKS, AKS, GKE, and RKE2/Rancher tables so all tables follow the same formatting as the Kubernetes, TKGI, and TKG tables.
• Change "The table below lists" to "The tables below list" in the Tested distributions section intro, since the section contains multiple tables.

content/operate/kubernetes/architecture/_index.md

• Restore the Kubernetes release-cadence context to the Lifecycle section. The original ## Lifecycle paragraph was replaced with a CNCF-conformance statement that did not fit the heading. The CNCF note is preserved and integrated into the lifecycle framing, and the standalone CNCF paragraph already on the Kubernetes landing page (content/operate/kubernetes/_index.md) is unaffected.

Out of scope

Other issues identified during review (for example, the pre-existing malformed 6.2.10-45 header cell, duplicate rows in the Rancher table, the missing table-scrollable wrapper on the VKS table, and auto-generated grammar/line-break issues in the API reference files) are not addressed here.

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Pull Request opened by Augment Code with guidance from the PR author

[github-actions]

Staging links:
https://redis.io/docs/staging/fix/content/operate/kubernetes/architecture/
https://redis.io/docs/staging/fix/content/operate/kubernetes/reference/supported_k8s_distributions/

[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

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^{Security scan by Jit}