fix order of html tags when if in key block

[tanhauhau]

Fixes #5680

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

[benmccann]

eslint enforces a new line at the end of files, but it looks like we have only set it up to run against js and ts files (probably because we have some .svelte files in the test with purposefully malformed content for testing)

[Conduitry]

eslint-plugin-svelte3 wouldn't complain about this anyway. The linting rules just apply to the parts that are JS (the script tags and the template expressions), and it doesn't extrapolate any of them to the component itself.

[Conduitry]

@benmccann I see you added the feature: each tag to this. I don't have especially strong opinions about this, but this issue/PR is actually about {#key}, not a keyed {#each}. Did you pick feature: each because it seemed like the best fit out of what there is currently? Might a new tag be warranted?

[benmccann]

Ah, yeah. I didn't look that closely and assumed it was keyed each especially since it was the closest match. I didn't realize there was a key feature. We could add a new label, but I think the existing labels might be a bit granular and a better solution could be to come up with some higher-level categories for the labels to use