manual_unwrap_or: Try suggesting map_or when unwrap_or fails

[tesuji]

changelog: [manual_unwrap_or]: Try suggesting map_or when unwrap_or fails

Next step of #13061

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[Alexendoo]

option_if_let_else covers this, manual_unwrap_or shouldn't suggest other methods

[tesuji]

I think you're right. Since option_if_let_else is allowed by default, I cound't find out that this suggestion clashes with it.
Closing this PR then.