sway-lsp: remove second read from hover_data that can deadlock

[scaspin]

Description

Fix #7711

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
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[fuel-cla-bot]

Thanks for the contribution! Before we can merge this, we need @scaspin to sign the Fuel Labs Contributor License Agreement.

[cursor]

PR Summary

Low Risk
Single-line concurrency fix aligning with an existing code path; no behavior change beyond avoiding duplicate locking.

Overview
Fixes a potential deadlock in hover handling when a token has no separate declaration ident.

The None branch of hover_data was calling hover_format with &state.engines.read() even though the caller already holds an engines read lock and passes engines in. That redundant lock matches the Some(decl_ident) path, which already used the parameter—so hover no longer takes a second read on state.engines.

^{Reviewed by Cursor Bugbot for commit 2a1f164. Bugbot is set up for automated code reviews on this repo. Configure here.}

[codspeed-hq]

Merging this PR will not alter performance

✅ 25 untouched benchmarks

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_{Comparing scaspin:master (2a1f164) with master (ac418cc)}