Alert component inherits incorrect line height

Summary

When viewed on GitLab UI's Storybook, with and without GitLab's application CSS bundle, the alert component's line heights are correct.

When viewed in Pajamas, the line height that is inherited is wrong, leading to incorrect spacing (specifically compared to the alert icon).

Correct (Storybook)	Incorrect (Pajamas Design tab)	Incorrect (Pajamas Vue Component tab)

Basically, in the Design tab in Pajamas, the inherited line-height value is 28px; in the Vue Component tab, it's 16px. In Storybook, the inherited value is 1.5

This issue may actually belong in the gitlab-ui project, depending on what the best fix is.

Possible fixes

I'm not a fan of either of these really, but anyway:

1. Specify the line-height specifically in the alert component's styles.
   • This seems to be what some components do, but not all.
   • This seems a bit like overkill, as line-height is naturally inherited, and so in theory every component would have to specify a line-height to avoid this.
2. Align the line-heights specified in Pajamas with those in GitLab and gitlab-ui.
   • This would in theory fix similar problems for all components.
   • This doesn't fix the root problem, which is CSS bleed.