[OUDS] fix(download app page): Improve accessibility

[hannahiss]

Types of change

• Non-breaking change
• Breaking change (fix or feature that would change existing functionality and usage)

Related issues

Closes #3330

Context & Motivation

Improve accessibility (after Vincent Aniort review) and enhance use of components and utilities

Description

Fix some accessibility issues:

• the QR code has an aria-labelledby pointing toward nothing => it is pointing to the SVG title (first tag inside the <svg>. It works well with NVDA and Talkback) Is it allright to keep it that way @Aniort?
• perhaps the QR code should enlarge with the zoom text only => ok, size is now set in rem (the image is not so big in 200% text zoom so it seems ok to enlarge it)
• add aria-hidden for the whole carousel => ok, aria-hidden added plus alt texts on images removed

Some other enhancements:

• remove useless xmlns="http://www.w3.org/2000/svg", since it is already set in the first <svg> tag, and the other are pointing on it
• replace old class hxl-md-icon by a correct one (decorative-xlarge-icon)
• replace old class bl-md-icon by a correct one (decorative-medium-icon)
• remove useless width and height attributes since they are set by icon size utilities classes
• remove useless (and non-existing) btn-large class
• remove useless class me-2xsmallon icons inside buttons
• use an icon size utility class when it was not the case

Checklists

• I have read the contributing guidelines
• My change follows the developer guide
• My change pass all tests
• My change is compatible with a responsive display
• I have added tests (Javascript unit test or visual) to cover my changes
• My change introduces changes to the documentation that I have updated accordingly
  • Title and DOM structure is correct
  • Links have been updated (title changes impact links)
  • CSS for the documentation
• I have checked all states and combinations of the component with my change
• I have checked all the impacts for the other components and core behavior (grid, reboot, utilities)

Checklist (for Core Team only)

• The changes need to be in the migration guide
• The changes are well displayed in Storybook (be careful if example order has changed for DSM)
• The changes are compatible with RTL
• Manually test browser compatibility with BrowserStack (Chrome 120, Firefox 121, Edge 120, Safari 15.6, iOS Safari, Chrome & Firefox on Android)

Progression (for Core Team only)

• Code review
• Design review
• A11y review
• Commit on ouds/main following conventional commit

Live previews

• https://deploy-preview-3337--boosted.netlify.app/orange/docs/1.0/examples/download-app/
• https://deploy-preview-3337--boosted.netlify.app/sosh/docs/1.0/examples/download-app/

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[MaxLardenois]

LGTM