[lacros] Enable tree closing for linux-lacros-builder-rel

It's been ~1 week on CI/CQ and the builder is stable.

Bug: 1104291
Change-Id: I546734d0719faa1d48db4910ff2db14b11b7bdd4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2378617Reviewed-by: Yuke Liao <liaoyuke@chromium.org>
Commit-Queue: Sven Zheng <svenzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802113}

infra/config/generated/luci-notify.cfg

@@ -2912,6 +2912,25 @@ notifiers {
     failed_step_regexp: "bot_update|compile|gclient runhooks|runhooks|update"
   }
 }
+notifiers {
+  notifications {
+    on_occurrence: FAILURE
+    failed_step_regexp: "bot_update|compile|gclient runhooks|runhooks|update"
+    email {
+      rotation_urls: "https://chrome-ops-rotation-proxy.appspot.com/current/oncallator:chrome-build-sheriff"
+    }
+    template: "tree_closure_email_template"
+  }
+  builders {
+    bucket: "ci"
+    name: "linux-lacros-builder-rel"
+    repository: "https://chromium.googlesource.com/chromium/src"
+  }
+  tree_closers {
+    tree_status_host: "chromium-status.appspot.com"
+    failed_step_regexp: "bot_update|compile|gclient runhooks|runhooks|update"
+  }
+}
 notifiers {
   notifications {
     on_occurrence: FAILURE

infra/config/subprojects/chromium/ci.star

@@ -1207,8 +1207,6 @@ ci.chromiumos_builder(
     ),
     cq_mirrors_console_view = settings.cq_mirrors_console_name,
     main_console_view = settings.main_console_name,
-    # TODO(crbug.com/1104291): Enable tree closing.
-    tree_closing = False,
 )
 
 ci.chromiumos_builder(