Adding new styles for dashboard notifications.

Change the reverification failure message styling.

Changing templates so new styles do not appear in courseware.

Removing unused aria tag.

PR comments on cleaning up SASS

Fix signup LMS test.

Copy changes per review on PR

Updating based on PR comments

Style and HTML changes for notifications
Merge pull request #5497 from edx/sanchez/update-message-styles

Adding new styles for dashboard notifications.