Add OOM canary settings page to the sidebar

[fastio]

The new OOM canary documentation page is added to ClickHouse/ClickHouse in
ClickHouse/ClickHouse#107465. This adds the matching
sidebar entry so the page is not flagged as a "floating" page by the docs build.

Merge order: the docs build copies the English docs from ClickHouse/ClickHouse
master, where oom-canary.md does not exist yet, so CI here will fail with a
dangling sidebar reference until that PR is merged into master. Please merge this
after ClickHouse/ClickHouse#107465.

Related: ClickHouse/ClickHouse#107465

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Note

Low Risk
Single sidebar entry with no runtime or application logic; CI may fail temporarily until the synced doc file exists upstream.

Overview
Adds operations/settings/oom-canary to the Settings section of the serverAdmin sidebar in sidebars.js, placed after memory overcommit so the new OOM canary doc is linked in navigation instead of being treated as a floating page.

This is a navigation-only change; the markdown page is introduced in ClickHouse/ClickHouse and is expected to land via the docs sync. Until that upstream doc exists on master, the docs build may fail on a dangling sidebar reference—merge after the companion ClickHouse PR.

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