Fix typo in exercise-1 p4tutorial

Change-Id: Ifc6acc211b46668dc7c20b858eaa090dda9c7f18
diff --git a/apps/p4-tutorial/exercise-1.md b/apps/p4-tutorial/exercise-1.md
index 2ebba43..f796588 100644
--- a/apps/p4-tutorial/exercise-1.md
+++ b/apps/p4-tutorial/exercise-1.md
@@ -368,9 +368,9 @@
 
     Enter the following command to **activate the web interface**:
 
-        ```
-        onos> app activate org.onosproject.gui
-        ```
+    ```
+    onos> app activate org.onosproject.gui
+    ```
 
     Open a browser from within the tutorial VM (e.g. Firefox) to
     <http://127.0.0.1:8181/onos/ui/>. When asked, use the username `onos`