Revert "upload failing screenshots for firefox tests"

This reverts commit ab335dff6356e379e874d608638ced1f047e7eb4.

Reason for revert: the golden files upload needs to check the command is not running with led. Led always use a buildbucket id which fails trying to delete previous files. https://ci.chromium.org/p/flutter/builders/try/recipes-with-led/b8866499872050734912?
Original change's description:
> upload failing screenshots for firefox tests
>
> Change-Id: I1928624db2fe523ad6882f8f428c486de75ba662
> Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/7420
> Reviewed-by: Christopher Fujino <fujino@google.com>
> Commit-Queue: Nurhan Turgut <nurhan@google.com>

TBR=godofredoc@google.com,flutter-scoped@luci-project-accounts.iam.gserviceaccount.com,fujino@google.com,nurhan@google.com

Change-Id: I71520cc84a89c6217b2f912ab600578cd7bf3df5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/7461
Reviewed-by: Godofredo Contreras <godofredoc@google.com>
Commit-Queue: Godofredo Contreras <godofredoc@google.com>