perf: remove chai as a direct dependency, keep it in @vitest/expect

[sheremet-va]

Description

We were also installing chai in both @vitest/expect and vitest. This duplicated the amount of work Node.js needs to do. Removing chai from vitest (but keeping it in expect) removes ~10ms at startup for every test file.

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[AriPerkkio]

Latest ^5 and 6 versions should be good now, no need for bundling.

const startTime = performance.now();

await import("chai");
// "chai": "5.2.1" > 4.39 ms
// "chai": "5.3.1" > 13.52 ms
// "chai": "5.3.2" > 2.92 ms
// "chai": "6.0.0" > 2.87 ms

console.log(`${(performance.now() - startTime).toFixed(2)} ms`);

[sheremet-va]

Sounds good. Let's keep chai in dependencies.