[3xh] Remove no longer existing test_suite

Test suite hostonly_devicelab_tests got removed in:
https://github.com/flutter/flutter/commit/fd0e223b74f983ef04a681e99df3f8fd95de3252

Change-Id: I06574606a19ca92bc1f644800d4c00c8af5470c7
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/164920
Auto-Submit: Daco Harkes <dacoharkes@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
4 files changed