CAMEL-23461: docs - sync 4.18 upgrade-guide entry to main for camel-aws-bedrock

[oscerd]

Doc-sync follow-up for #23161

Adds the camel-aws-bedrock upgrade-guide entry to main's
docs/user-manual/modules/ROOT/pages/camel-4x-upgrade-guide-4_18.adoc to match the entry that
shipped on the camel-4.18.x branch via the backport PR #23161 (merged as e22edbb5).

Why

Per the project's backport upgrade-guide policy:

The docs/user-manual/modules/ROOT/pages/camel-4x-upgrade-guide-4_XX.adoc files for ALL versions
live on main and act as the canonical history across all releases. When a PR is backported to a
maintenance branch and adds an upgrade-guide note for that release line, the corresponding entry
must ALSO be added to the matching camel-4x-upgrade-guide-4_XX.adoc file on main — either as
part of the backport workflow or in a follow-up doc-sync PR.

Without this sync, main's 4.18 upgrade guide drifts out of sync with what is actually shipping on
the camel-4.18.x maintenance branch.

Original work

• Original fix on main: CAMEL-23461: camel-aws-bedrock - applyGuardrail reads guardrail identifier from wrong header #23151 — CAMEL-23461: camel-aws-bedrock - applyGuardrail reads guardrail identifier from wrong header
• Backport to camel-4.18.x: [backport camel-4.18.x] CAMEL-23461: camel-aws-bedrock - applyGuardrail reads guardrail identifier from wrong header #23161 (merged)
• JIRA: https://issues.apache.org/jira/browse/CAMEL-23461

Change

Docs-only: a single === camel-aws-bedrock section is inserted into the "Upgrading from 4.18.1 to
4.18.3" block, placed before === camel-hazelcast to match the ordering on the camel-4.18.x
branch. The wording is identical to the entry shipped on camel-4.18.x. No code changes.

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Claude Code on behalf of Andrea Cosentino.

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