sway-lsp: Fix the double read-lock bug in session

[Chain-Fox]

Description

Fix #7144

way-lsp contains a possible double read-lock bug.

The lock is a parking_lot::RwLock:
The first read lock is on L227 in completion_items
The second read lock is on L235 in completion_items

sway/sway-lsp/src/core/session.rs

Lines 227 to 235 in 324f04f

	let engines = self.engines.read();
	let fn_tokens =
	self.token_map
	.tokens_at_position(&engines, uri, shifted_position, Some(true));
	let fn_token = fn_tokens.first()?.value();
	let compiled_program = &*self.compiled_program.read();
	if let Some(TypedAstToken::TypedFunctionDeclaration(fn_decl)) = fn_token.as_typed() {
	if let Some(program) = &compiled_program.typed {
	let engines = self.engines.read();

The solution is to remove the redundant second read lock
After the fix, the possible double read-lock will be eliminated, and the performance may be better.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[fuel-cla-bot]

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

[JoshuaBatty]

Thanks for the PR. It does seem like this line was unnecessary

[codspeed-hq]

CodSpeed Performance Report

Merging #7145 will not alter performance

_{Comparing Chain-Fox:double-lock-fix (2d036f8) with master (324f04f)}

Summary

✅ 22 untouched benchmarks