Enable `chromium.resultdb.result_sink` experiment on chromium fyi builders at 30%

Bug: 1108016
Change-Id: I1d394ec317ec1674905c1dfd92e83e5547d033fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2441737Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: Chan Li <chanli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812911}

infra/config/lib/ci.star

@@ -682,6 +682,11 @@ def fyi_builder(
         builder_group = "chromium.fyi",
         execution_timeout = execution_timeout,
         goma_backend = goma_backend,
+        # TODO(crbug.com/1108016): Move this kwarg to ci.builder(), after
+        # ResultSink and result_adapter is confirmed to work.
+        experiments = {
+            "chromium.resultdb.result_sink": 30,
+        },
         **kwargs
     )