Ignore _to_string lints in code from_expansion

[future-highway]

Includes the string_to_string and str_to_string lints.

changelog: [str_to_string]: Ignore code from expansion
changelog: [string_to_string]: Ignore code from expansion

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Manishearth (or someone else) some time within the next two weeks.

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[Manishearth]

@bors r+

[bors]

📌 Commit cd00f5b has been approved by Manishearth

It is now in the queue for this repository.

[bors]

⌛ Testing commit cd00f5b with merge 68dbc84...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Manishearth
Pushing 68dbc84 to master...