fixed issue

Author: Manjusha.S

app/code/Magento/Checkout/Test/Mftf/Test/StorefrontGuestCheckoutDataPersistTest.xml

@@ -19,6 +19,7 @@
             <group value="checkout"/>
         </annotations>
         <before>
+            <magentoCLI command="config:set {{EnableFlatRateConfigData.path}} {{EnableFlatRateConfigData.value}}" stepKey="enableFlatRate"/>
             <createData entity="_defaultCategory" stepKey="createCategory"/>
             <createData entity="_defaultProduct" stepKey="createProduct">
                 <requiredEntity createDataKey="createCategory"/>