fix(ui-alerts,console): remove Alert live-region role warning

[ToMESSKa]

INSTUI-5131

ISSUE:

• Alert warns that your live region must have role="alert", but role="alert" means assertive per WAI-ARIA, so even when you'd set liveRegionPoliteness="polite" (non-assertive), you got a warning asking for role="alert". It was likely a leftover before the liveRegionPoliteness prop was added. GitHub issue: Alert wants role="alert" added to live region #2276

Setting role="alert" is equivalent to setting aria-live="assertive" and aria-atomic="true". [...] Dynamic changes that are less urgent should use a less aggressive method, such as including aria-live="polite" or using an other live region role like status.
https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Reference/Roles/alert_role

TEST PLAN:

• run it locally
• add this to packages/__docs__/src/index.html after line 4 (webpack 5 doesn't provide process in the browser so typeof process resolves to "undefined" in packages/console/src/console.ts and log messages are not emitted)

     window.process = window.process || { env: {} }
    </script>
    <script>

• test this example, it should not emit a warning

<div>
  <div className="alerts-container" id="live-region"></div>
  <Alert
    variant="info"
    renderCloseButtonLabel="Dismiss alert"
    liveRegion={() => document.getElementById("live-region")}
    liveRegionPoliteness="polite"
  >
    Just an alert.
  </Alert>
</div>

• if you revert the fix, the warning should reappear

[github-actions]

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[github-actions]

Visual regression report

⚠️ Changes detected.

Status	Count
Unchanged	0
Changed	1
New	96
Removed	32

📊 View full report

Diff images (33)

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_{Baselines come from the visual-baselines branch. They refresh on every merge to master.}

[matyasf]

see my comment

[matyasf]

hmm this is not the best description, its more complicated. Please add this:

<Figure.Item>
For the liveRegion DOM element, note that the role prop adds implicit ARIA attributes, but these are not applied, unless you set liveRegionPoliteness or isLiveRegionAtomic to undefined.
</Figure.Item>

[ToMESSKa]

@matyasf liveRegionPoliteness and isLiveRegionAtomic both have default values.

65    static defaultProps = {
...
72      liveRegionPoliteness: 'assertive', 
73      isLiveRegionAtomic: false,
...
76    }

So aria-live and aria-atomic are always explicitly set even if these props are undefined, e.g.:

<div>
  <div className="alerts-container" id="live-region"></div>
  <Alert
    variant="info"
    renderCloseButtonLabel="Dismiss alert"
    liveRegion={() => document.getElementById("live-region")}
  >
    Just an alert.
  </Alert>
</div>