Revert "[infra] Add back generate_buildfiles.py to gclient hooks"
Revert "[infra] Add back generate_buildfiles.py to gclient hooks"

This reverts commit 9ed26558f137f77c8ff8c82217d86c3630ac304f.

Reason for revert: Failing builds due to missing gn runs

Original change's description:
> [infra] Add back generate_buildfiles.py to gclient hooks
> 
> Omitting this was a little fragile. We can add it back following the
> fix in https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1255446
> 
> Change-Id: Idfa0a08674bc1ea7ef19d7c9a96e17e6da293297
> Reviewed-on: https://dart-review.googlesource.com/c/84280
> Reviewed-by: Alexander Thomas <athom@google.com>
> Commit-Queue: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>

TBR=whesse@google.com,sortie@google.com,9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com,athom@google.com

Change-Id: I87cd9ddf5eca2e2a247a74eb1e666aa40bae7a48
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/84281
Reviewed-by: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>
Commit-Queue: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>

dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk