[fix] rendering void tag for <svelte:element>

[baseballyama]

fix: #7449

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
• Prefix your PR title with [feat], [fix], [chore], or [docs].
• 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

[tanhauhau]

@baseballyama usually when there's new commit on the master branch, I dont merge master into my branch, instead i rebase my branch onto the latest master branch. This allows me to have a cleaner, linear history on the branch, and allowing me to squash all the changes during merging the PR.

[baseballyama]

OK, I will use rebase on Svelte repository.

Since now I did not use rebasing on Svelte after starting PR, because it become unable to know where is a new change, and I felt that merging was often used in sveltejs repositories.

[baseballyama]

@tanhauhau

Thank you for updating it!

[baseballyama]

I rebased it on master branch because conflict is there.