Revert "scanner: Add debug command line flag to override Scanner disclaimer"

This reverts commit 4bf5368c24eb42b1cd1548790ec776c7458792f3.

Reason for revert: Removing debug flag that isn't used any more

Original change's description:
> scanner: Add debug command line flag to override Scanner disclaimer
>
> This is useful for developers and a11y testing.
>
> Bug: b:402981629
> Change-Id: I6a6a21003b174b0fff27eee21c4ae557f6bab7a8
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6356547
> Commit-Queue: Michael Cui <mlcui@google.com>
> Reviewed-by: Michelle Chen <michellegc@google.com>
> Cr-Commit-Position: refs/heads/main@{#1433888}

Bug: 427257915, b:402981629
Change-Id: I2d46dce9b15afbd14ede8a28b2bcce353c64f3e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6680708
Reviewed-by: Michelle Chen <michellegc@google.com>
Commit-Queue: Michael Cui <mlcui@google.com>
Cr-Commit-Position: refs/heads/main@{#1479666}