chore: Clarify IP address format guidelines

[ald8]

Proposed changes

Clarify ipAddress value format in https://docs.nginx.com/waf/policies/ip-address-lists/.

The existing docs mentioned a single host with explicit mask /32 without explaining what values are actually accepted, leading to confusion (e.g., 1.2.3.4/28 rejected at policy import).

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Footnotes

1. Potentially sensitive information includes personally identify information (PII), authentication credentials, and live URLs. Refer to the style guide for guidance about placeholder content. ↩

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[ald8]

I have hereby read the F5 CLA and agree to its terms

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