MzpNotification adds `cta` anchor after the paragraph

[janbrasna]

The title and cta would normally (as shown in other examples) end up in the same paragraph:

protocol/components/notification-bar/notification-bar--scripted.readme.md

Lines 28 to 42 in e5627f8

	MzpNotification.init(origin, options);
	```
	You can also pass a range of configuration options:
	```javascript
	MzpNotification.init(origin, {
	title: 'This is the title.',
	cta: {
	text: "And this is a CTA link.",
	url: "https://www.mozilla.org",
	attrs: {"target": "_blank", "rel": "noopener"}
	},
	className: 'mzp-t-warning',
	closeText: 'Close notification',

This is how it is rendered:

<aside class="mzp-c-notification-bar mzp-t-warning mzp-is-sticky">
  <button class="mzp-c-notification-bar-button" type="button" title="Close notification">Close notification</button>
  <p>This is the title.</p>
  <a href="https://www.mozilla.org" class="mzp-c-notification-bar-cta" target="_blank" rel="noopener">And this is a CTA link.</a>
</aside>

When fixing #1040, I regressed to #559:

(expand for before/after screenshots)

(before:)

(after:)

It would seem mzp-c-notification-bar-cta was never styled explicitly, so I think additional #1000 (comment) for resilience is in order to render the expected spacing.

[janbrasna]

Since title is mandatory, even if it was only whitespace it should be expected to emit its paragraph. In #1040@54c24e4 I have built upon this assumption, rendering the title and cta contents next to each other in the same paragraph. Worstcase there would be just some extra whitespace emitted, that's ignored when rendered.