[infra] Do not print all test results in front-end unit tests

Change-Id: I0236a0587882ecfe4ad33b094e5d6dd26e08dad2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/166104
Reviewed-by: Jens Johansen <jensj@google.com>
Commit-Queue: Karl Klose <karlklose@google.com>
diff --git a/tools/bots/test_matrix.json b/tools/bots/test_matrix.json
index 605c4d5..1115d5e 100644
--- a/tools/bots/test_matrix.json
+++ b/tools/bots/test_matrix.json
@@ -891,8 +891,7 @@
           "testRunner": true,
           "arguments": [
             "pkg/front_end/test/unit_test_suites.dart",
-            "-ncfe-unittest-asserts-${mode}-${system}",
-            "--verbose"
+            "-ncfe-unittest-asserts-${mode}-${system}"
           ]
         }
       ]