docs: useSignal$ typo

[reemardelarosa]

What is it?

• [ ] Feature / enhancement
• [ ] Bug
• [x] Docs / tests

Description

useSignal()

Use cases and why

From: useSignal$

To: useSignal

Checklist:

• [x] My code follows the developer guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [ ] Added new tests to cover the fix / functionality

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