refactor: use slices.Equal to simplify code

[xixishidibei]

Related Issues

Proposed Changes

There is a new function added in the go1.21 standard library, which can make the code more concise and easy to read.

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[Copilot]

Pull Request Overview

This PR refactors the TipSet.Equals method to use the new standard library function slices.Equal, simplifying the code and improving readability.

• Replaces manual loop with slices.Equal for slice comparison.
• Adds the slices import to support the new function.