Switch to experimental config for v8 autopush

This enables https://skia-review.git.corp.google.com/c/buildbot/+/1240516 + https://chrome-internal-review.git.corp.google.com/c/infra/infra_internal/+/9313760, starting an experiment with compound checks.

Change-Id: I9ba4a04d618a0f9409b22a32f9d8f6147256aeb8
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/1240517
Reviewed-by: Maxim Sheshukov <maximsheshukov@google.com>
Commit-Queue: Anri Sidorov <ansid@google.com>

perf/configs/spanner/v8-internal-autopush.json

diff --git a/perf/configs/spanner/v8-internal-autopush.json b/perf/configs/spanner/v8-internal-autopush.json
index bab993a..b605bad 100644
--- a/perf/configs/spanner/v8-internal-autopush.json
+++ b/perf/configs/spanner/v8-internal-autopush.json
@@ -44,8 +44,8 @@
   },
   "maintenance_config": {
     "gitiles_repo_url": "https://chrome-internal.googlesource.com/infra/infra_internal",
-    "sheriff_config_path": "infra/config/generated/skia-sheriff-configs.cfg",
-    "fallback_to_lucicfg": true
+    "sheriff_config_path": "infra/config/subprojects/skiaperf/v8-perf-autopush.textpb",
+    "fallback_to_lucicfg": false
   },
   "git_repo_config": {
     "provider": "gitiles",