[resultdb] enable ResultDB on FYI.LocalGTests at 30%

https://crrev.com/c/2570155 added the experiment flag for launching
local gtests with ResultDB.
This CL sets the flag to enable ResultDB on FYI at 30%.

Bug: 1084332
Change-Id: I530ce7f74599f2dce5b52ff381778a11d35da368
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2582809
Commit-Queue: Scott Lee <ddoman@chromium.org>
Reviewed-by: Chan Li <chanli@chromium.org>
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841241}

infra/config/lib/ci.star

@@ -368,6 +368,9 @@ def fyi_builder(
         builder_group = "chromium.fyi",
         execution_timeout = execution_timeout,
         goma_backend = goma_backend,
+        experiments = {
+            "chromium.resultdb.result_sink.gtests_local": 30,
+        },
         **kwargs
     )