Vue: fix format on blocks with src attribute

[fisker]

Fixes #9049

• I’ve added tests to confirm my change works.
• (If changing the API or CLI) I’ve documented the changes I’ve made (in the docs/ directory)
• (If the change is user-facing) I’ve added my changes to changelog_unreleased/*/pr-XXXX.md file following changelog_unreleased/TEMPLATE.md.
• I’ve read the contributing guidelines.

✨Try the playground for this PR✨

[thorn0]

Even though it might be not very useful code, this looks strange:

Prettier pr-9052
Playground link

--parser vue

Input:

<custom lang="markdown" />

Output:

<custom lang="markdown"

/>

[fisker]

I'll send another PR for this.