[dartdevc] prune unneeded bot configs
[dartdevc] prune unneeded bot configs

The modular tests run on d8 - no need to run on both chrome and ff bots.

Old DDC is only used internally on Linux today, so removing Mac tests.
(Could also split out Win testing.)

Change-Id: If2ab50fae89d25d95f2e45d80de4834033e43b9f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/114621
Reviewed-by: Nicholas Shahan <03847abd2d8aadfe859ecb98095a31f9f515dc47@google.com>
Reviewed-by: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@google.com>
Commit-Queue: Vijay Menon <671ecbb18d31a1c038875027dcfe976af959ea9f@google.com>

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