Hide empty headers across admin using aria-hidden

[Jaivignesh-afk]

Fixes #11596

Added aria-hidden="true" to empty headers across admin as mentioned in https://github.com/wagtail/wagtail/issues/11596#issue-2119724365

Updated Jest snapshots for js files Added django template comments for html files

OS:Ubuntu Browser : Brave Please check the following:

• [x] Do the tests still pass?[^1]
• [x] Does the code comply with the style guide?
  • [ ] Run make lint from the Wagtail root.
• [ ] For Python changes: Have you added tests to cover the new/fixed behaviour?
• [ ] For front-end changes: Did you test on all of Wagtail’s supported environments?[^2]
  • [ ] Please list the exact browser and operating system versions you tested:
  • [ ] Please list which assistive technologies [^3] you tested:
• [ ] For new features: Has the documentation been updated accordingly?

Please describe additional details for testing this change.

[^1]: Development Testing [^2]: Browser and device support [^3]: Accessibility Target

[squash-labs[bot]]

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