Fix an issue where system chat messages weren't announced

[vhuseinova-msft]

What

Steps to reproduce:

1. Start the chat app
2. Navigate to 'Start chat' button using tab key and activate it using enter key.
3. Navigate to 'Name' edit field using tab key and type a name.
4. Navigate to 'Join chat' button using tab key and activate it using enter key.
5. 'Your chat sample' app opens.
6. Let another user join the chat.
7. Observe the screen reader announcement. (expected result)
   Previous result: the system messages weren't announced.

Why

How Tested

Chat app

Process & policy checklist

• I have updated the project documentation to reflect my changes if necessary.
• I have read the CONTRIBUTING documentation.

Is this a breaking change?

• This change causes current functionality to break.

[github-actions]

Failed to pass the UI Test. If this PR is for UI change and the error is snapshot mismatch, please add "update_snapshots" label to the PR for updating the snapshot.

[github-actions]

Storybook 8 URL https://60c7ae6891f0e90039d7cd54-iezswmmvle.chromatic.com/

[github-actions]

@azure/communication-react jest test coverage for stable.

	Lines	Statements	Functions	Branches
Base	27517 / 43473 63.29%	27517 / 43473 63.29%	771 / 1368 56.35%	2327 / 3646 63.82%
Current	27510 / 43485 63.26%	27510 / 43485 63.26%	771 / 1368 56.35%	2293 / 3623 63.29%
Diff	-7 / 12 -0.03%	-7 / 12 -0.03%	0 / 0 0%	-34 / -23 -0.53%

[github-actions]

@azure/communication-react jest test coverage for beta.

	Lines	Statements	Functions	Branches
Base	55380 / 90379 61.27%	55380 / 90379 61.27%	1147 / 2589 44.3%	3418 / 5574 61.32%
Current	55376 / 90392 61.26%	55376 / 90392 61.26%	1147 / 2589 44.3%	3393 / 5561 61.01%
Diff	-4 / 13 -0.01%	-4 / 13 -0.01%	0 / 0 0%	-25 / -13 -0.31%

[github-actions]

Failed to pass the UI Test. If this PR is for UI change and the error is snapshot mismatch, please add "update_snapshots" label to the PR for updating the snapshot.

[github-actions]

Storybook 8 URL https://60c7ae6891f0e90039d7cd54-prcfyjcrqy.chromatic.com/

[palatter]

Looks good.

[github-actions]

CallWithChat bundle size is not changed.

• Current size: 11767078
• Base size: 11767078
• Diff size: 0

[github-actions]

Chat bundle size is increased❗.

• Current size: 1762514
• Base size: 1762338
• Diff size: 176

[github-actions]

Calling bundle size is not changed.

• Current size: 11767065
• Base size: 11767065
• Diff size: 0

[github-actions]

Storybook 8 URL https://60c7ae6891f0e90039d7cd54-xyehagsmtl.chromatic.com/