[dartdevc] skip co19 tests on linux bots
[dartdevc] skip co19 tests on linux bots

These tests aren't quite working yet, and they're causing delays in the
deflake step.

Change-Id: Ic037858e4778a128403c80f1c0356c6dd91cb831
Reviewed-on: https://dart-review.googlesource.com/c/92241
Commit-Queue: Jenny Messerly <6285f43aa2dd0931180012d62b847adf2c37a418@google.com>
Reviewed-by: Jenny Messerly <6285f43aa2dd0931180012d62b847adf2c37a418@google.com>

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