[Doc-Schema] [Accessibility] `imageAltText` is defined but not used in places where `image` is used

[compulim]

Version

Current version of schema.

Describe the bug

In the schema section imageAltText, it stated how image, imageAltText and title is defined.

However, in the card actions (Message Back, IM Back, Post Back, etc), only image and title are used. imageAltText is not used in any part of the schema.

I believe imageAltText should be used in where image is used.

To Reproduce

(No repro steps for docs)

Expected behavior

The imageAltText field should be used in place where the image field is used, such as Message Back, IM Back, Post Back, where they all have the image fields.

Screenshots

No screenshots for doc issues.

Additional context

No additional context.

Tracking Status

Dotnet SDK TODO

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Javascript SDK TODO

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Python SDK TODO

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Java SDK TODO

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Samples TODO

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Docs TODO

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Tools TODO

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