fix(alert): no wrapper class when no message provided

[billhimmelsbach]

Currently when there's no message but has children (explanations), then a m-notification_explanation applied which makes it not possible to achieve designs like these (unbolded, aligned text):

Changes

• if there is no message, but still has children then do not apply m-notification_explanation to allow alert flexibility

How to test this PR

1. Do the tests pass?
2. How do the examples look?
3. Try modifying the package.json to point the DSR to this commit and see how the alerts are affected.

Screenshots

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[meissadia]

Looks good! 👍🏾