chore: mark nest method this: void for destructing safely

[JounQin]

close sveltejs/eslint-plugin-svelte3#102

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with npm test and lint the project with npm run lint

[frederikhors]

Thank you @JounQin and @dummdidumm, can we merge and release this please? I have dozens of projects with thousands of warnings in CI! 🤣

[JounQin]

@dummdidumm Can this PR been merged?