Correct class name formatting in locking.md

[PhantomWatson]

`class` Cake\Lock\**Lock**

was making the lock page's header show up as

[Copilot]

Pull request overview

This PR updates the Locking documentation page’s “class” header line to avoid malformed rendering caused by the previous mixed Markdown formatting.

Changes:

• Replace the class header line in locking.md to correct how the class name is displayed.

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[dereuromark]

The render glitch comes from the single backslash: \L is treated as a Markdown escape, which eats the L and breaks the header. Dropping the bold isn't needed — the real fix is to escape the namespace separators and keep the short class name bold, matching every other page (e.g. caching.md:8 → Cake\\Cache\\**Cache**, views.md:8 → Cake\\View\\**View**).

`class` Cake\\Lock\\**Lock**

That keeps locking.md consistent with the rest of the docs.