[infra] Fix test.dart saying untested configurations don't exist.

There are more named configurations in existance than the ones that actually
run on the builders.

Change-Id: Ie91e71fcec6014830fe286b33c856177fb30c2a2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/96380
Reviewed-by: Alexander Thomas <athom@google.com>
diff --git a/tools/test.dart b/tools/test.dart
index 19de0fe..618c9fb 100755
--- a/tools/test.dart
+++ b/tools/test.dart
@@ -205,11 +205,6 @@
         "named configuration $requestedNamedConfiguration");
     return false;
   }
-  if (requestedNamedConfiguration != null && outputNamedConfiguration.isEmpty) {
-    stderr.writeln("error: The named configuration "
-        "$requestedNamedConfiguration doesn't exist");
-    return false;
-  }
   if (requestedNamedConfiguration != null && outputBuilders.isEmpty) {
     stderr.writeln("error: The named configuration "
         "$requestedNamedConfiguration isn't tested on any builders");