DR-2464 hero component VQA and Accessibility updates

[avertrees]

Ticket:

• JIRA ticket DR-2464

This PR does the following:

• Updates the alt text for the image in the Hero Component to use the title of the featured item instead of "example image." Note: this is currently hard coded and will need to update this to be dynamic when we implement the featured item tickets.
• Added an aria label for the "Learn more" link with the text "Learn more about harmful content".
• Updated the Heading (desktop) and Heading (desktop) to be 54px and 42px, respectfully, by using the size "heading2"

How has this been tested?

Accessibility concerns or updates

Checklist:

• I have added relevant accessibility documentation for this pull request.
• All new and existing tests passed.

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Name	Status	Preview	Comments	Updated (UTC)
digital-collections	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 25, 2023 5:11pm