docs: Clean up toThrowError documentation

[erikpukinskis]

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Hi there! This is my first Vitest PR, so apologies in advance if I get any of the process wrong. I did ready the contributing guidelines.

This is just a documentation change. I was using toThrowError incorrectly, and I thought there were a couple fixes to the documentation that could've helped me:

• Note that toThrowError is an alias of toThrow
• Fix confusing paragraph order
• Fix broken link to #toThrow
• Note that toThrow, toThrowError, toThrowErrorMatchingSnapshot, and toThrowErrorMatchingInlineSnapshot must be used in conjunction with .rejects when used with async functions