Revert "Manual engine roll with disabled service authentication codes (#30919)" (#30930)

This reverts commit 19d6e7b6.

bin/internal/engine.version

-ae4df6fd189219fc35b27cd5e014bd8445c4e59d
+72986c39ea3669ef26d4d7d7cd0c44f513fcd117

dev/devicelab/lib/framework/runner.dart

@@ -32,7 +32,6 @@ Future<Map<String, dynamic>> runTask(String taskName, { bool silent = false }) a
   final Process runner = await startProcess(dartBin, <String>[
     '--enable-vm-service=0', // zero causes the system to choose a free port
     '--no-pause-isolates-on-exit',
-    '--disable-service-auth-codes', // TODO(bkonyi): enable auth codes
     taskExecutable,
   ]);
 
@@ -164,4 +163,4 @@ Future<void> cleanupSystem() async {
   } else {
     print('Could not determine JAVA_HOME; not shutting down Gradle.');
   }
-}
+}
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