vm_shell: Fix wrong example in help message

The argument '--cpu' isn't supported.

Bug: 381182837
Test: vm_shell start-microdroid -- --protected --debug full
Change-Id: I2bd5b5f93bd5c65adc1ed246745934d6a34fce54
diff --git a/android/vm/vm_shell.sh b/android/vm/vm_shell.sh
index b73a9dc..60d9329 100755
--- a/android/vm/vm_shell.sh
+++ b/android/vm/vm_shell.sh
@@ -30,7 +30,7 @@
     echo "        /apex/com.android.virt/bin/vm run-microdroid binary."
     echo ""
     echo "        E.g.:"
-    echo "            vm_shell start-microdroid -- --cpu 5"
+    echo "            vm_shell start-microdroid -- --protected --debug full"
     echo ""
     echo "        --auto-connect - automatically connects to the started VMs"
     echo ""