[management] Count the new setting in the Settings round-trip guard

Test_AccountSettings_SaveAndRetrieve asserts how many exported fields
types.Settings has, so that adding one forces whoever added it to confirm it
survives a save and reload. DebugBundleUploadURL made it 28 and the assertion
still said 27.

With the count corrected the test populates the new field too and passes on
sqlite, postgres and mysql, which is the confirmation the guard exists to get.

management/server/store/sql_store_test.go

@@ -331,7 +331,7 @@ func Test_AccountSettings_SaveAndRetrieve(t *testing.T) {
 		settings := types.Settings{}
 		numOfExportedFields, err := populateFields.PopulateAll(reflect.ValueOf(&settings).Elem())
 		assert.NoError(t, err)
-		assert.Equal(t, 27, numOfExportedFields)
+		assert.Equal(t, 28, numOfExportedFields)
 		account.Settings = &settings
 
 		err = store.SaveAccount(context.Background(), account)