Update ML Challenge banner

[bchu1]

#1440

This should be merged right before 1/15.

Makes some code simplifications:

• Removes timer logic. We can just make the changes manually before the dates when the banner needs to be updated. This is so we have more testability and control over the code. Product also did not request any countdown text in the final copy.
• Removes usage of poorly documented third party hook, just uses localStorage directly.
• Switches from using 1 localStorage key to keep track of the last dismissed banner version to using separate keys for each banner version.

There's an unrelated test failure due to a current mismatch in BE staging data between V1 and V2.

[github-actions]

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https://bchu-banner.cryoet.dev.si.czi.technology

Updated: 01/10/25 @ 12:07:43 PM PST