Fix scoped labels to render tooltips correctly

Fixes #263773 (closed)

What does this MR do and why?

It was found that DOMPurify (which is used by v-safe-html) strips off attribute completely if it contains any self-closing tag. The scoped label tooltip template uses <br /> which gets removed when passed through v-safe-html. Hence the tooltips are not getting rendered correctly, as shown at #263773 (closed).

This MR replaces <br /> with <br> which is a valid HTML element - https://developer.mozilla.org/en-US/docs/Web/HTML/Element/br which should fix the underline issue.

Screenshots or screen recordings

How to set up and validate locally

1. Create a scoped label with some description.
2. Apply this label to any MR / Issue.
3. The applied label should render the tooltip now.

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